APOE is an apolipoprotein, a protein associating with lipid particles, that mainly functions in lipoprotein-mediated lipid transport between organs via the plasma and interstitial fluids (PubMed:14754908, PubMed:1911868, PubMed:6860692). APOE is a core component of plasma lipoproteins and is involved in their production, conversion and clearance (PubMed:14754908, PubMed:1911868, PubMed:1917954, PubMed:23620513, PubMed:2762297, PubMed:6860692, PubMed:9395455). Apolipoproteins are amphipathic mole

SecretedSecreted, extracellular spaceSecreted, extracellular space, extracellular matrixExtracellular vesicleEndosome, multivesicular body

Hyperlipoproteinemia 3

A disorder characterized by the accumulation of intermediate-density lipoprotein particles (IDL or broad-beta-lipoprotein) rich in cholesterol. Clinical features include xanthomas, yellowish lipid deposits in the palmar crease, or less specific on tendons and on elbows. The disorder rarely manifests before the third decade in men. In women, it is usually expressed only after the menopause.

Mitochondrial protein involved in the maturation of mitochondrial [4Fe-4S]-proteins in the late stage of the iron-sulfur cluster assembly pathway (PubMed:22323289, PubMed:23462291). Operates in cooperation with ISCA2 in the maturation of [4Fe-4S] proteins (PubMed:30269484) Involved in the maturation of mitochondrial 2Fe-2S proteins in the late stage of the iron-sulfur cluster assembly pathway

Mitochondrion

Multiple mitochondrial dysfunctions syndrome 3

A severe disorder of systemic energy metabolism, resulting in weakness, respiratory failure, lack of neurologic development, lactic acidosis, hyperglycinemia and early death. Some patients show failure to thrive, pulmonary hypertension, hypotonia and irritability. Biochemical features include severe combined deficiency of the 2-oxoacid dehydrogenases, defective lipoic acid synthesis and reduction in activity of mitochondrial respiratory chain complexes.

Hydrolyzes the galactose ester bonds of glycolipids such as galactosylceramide and galactosylsphingosine (PubMed:8281145, PubMed:8399327). Enzyme with very low activity responsible for the lysosomal catabolism of galactosylceramide, a major lipid in myelin, kidney and epithelial cells of small intestine and colon (PubMed:8281145, PubMed:8399327)

Lysosome

Krabbe disease

An autosomal recessive disorder characterized by insufficient catabolism of several galactolipids that are important for normal myelin production. Four clinical forms are recognized. The infantile form accounts for 90% of cases. It manifests before six months of age with irritability, spasticity, arrest of motor and mental development, and bouts of temperature elevation without infection. This is followed by myoclonic jerks of arms and legs, oposthotonus, hypertonic fits, and mental regression, which progresses to a severe decerebrate condition with no voluntary movements and death from respiratory infections or cerebral hyperpyrexia before 2 years of age. Cases with later onset present with unexplained blindness, weakness and sensorimotor peripheral neuropathy, mental deterioration and death.

Involved in endochondral bone formation as negative regulator of bone mineralization. Stimulates the proliferation of endothelial cells and promotes angiogenesis. Inhibits MMP9 proteolytic activity

Secreted, extracellular space, extracellular matrix

Lipoid proteinosis

Rare autosomal recessive disorder characterized by generalized thickening of skin, mucosae and certain viscera. Classical features include beaded eyelid papules and laryngeal infiltration leading to hoarseness. Histologically, there is widespread deposition of hyaline material and disruption/reduplication of basement membrane.

Intracellular cholesterol transporter which acts in concert with NPC1 and plays an important role in the egress of cholesterol from the lysosomal compartment (PubMed:11125141, PubMed:15937921, PubMed:17018531, PubMed:18772377, PubMed:29580834). Unesterified cholesterol that has been released from LDLs in the lumen of the late endosomes/lysosomes is transferred by NPC2 to the cholesterol-binding pocket in the N-terminal domain of NPC1 (PubMed:17018531, PubMed:18772377, PubMed:27238017). May bind

SecretedEndoplasmic reticulumLysosome

Niemann-Pick disease C2

A lysosomal storage disorder that affects the viscera and the central nervous system. It is due to defective intracellular processing and transport of low-density lipoprotein derived cholesterol. It causes accumulation of cholesterol in lysosomes, with delayed induction of cholesterol homeostatic reactions. Niemann-Pick disease type C2 has a highly variable clinical phenotype. Clinical features include variable hepatosplenomegaly and severe progressive neurological dysfunction such as ataxia, dystonia and dementia. The age of onset can vary from infancy to late adulthood.

Cleaves beta-linked terminal galactosyl residues from gangliosides, glycoproteins, and glycosaminoglycans Has no beta-galactosidase catalytic activity, but plays functional roles in the formation of extracellular elastic fibers (elastogenesis) and in the development of connective tissue. Seems to be identical to the elastin-binding protein (EBP), a major component of the non-integrin cell surface receptor expressed on fibroblasts, smooth muscle cells, chondroblasts, leukocytes, and certain cance

LysosomeCytoplasm, perinuclear region

GM1-gangliosidosis 1

An autosomal recessive lysosomal storage disease marked by the accumulation of GM1 gangliosides, glycoproteins and keratan sulfate primarily in neurons of the central nervous system. GM1-gangliosidosis type 1 is characterized by onset within the first three months of life, central nervous system degeneration, coarse facial features, hepatosplenomegaly, skeletal dysmorphology reminiscent of Hurler syndrome, and rapidly progressive psychomotor deterioration. Urinary oligosaccharide levels are high. It leads to death usually between the first and second year of life.

Catalyzes the phosphorylation of mevalonate to mevalonate 5-phosphate, a key step in isoprenoid and cholesterol biosynthesis (PubMed:11278915, PubMed:18302342, PubMed:9325256, PubMed:9392419)

CytoplasmPeroxisome

Mevalonic aciduria

Accumulation of mevalonic acid which causes a variety of symptoms such as psychomotor retardation, dysmorphic features, cataracts, hepatosplenomegaly, lymphadenopathy, anemia, hypotonia, myopathy, and ataxia.

Accepts electrons from ETF and reduces ubiquinone

Mitochondrion inner membrane

Glutaric aciduria 2C

An autosomal recessively inherited disorder of fatty acid, amino acid, and choline metabolism. It is characterized by multiple acyl-CoA dehydrogenase deficiencies resulting in large excretion not only of glutaric acid, but also of lactic, ethylmalonic, butyric, isobutyric, 2-methyl-butyric, and isovaleric acids.

Serves as the first electron transfer protein in all the mitochondrial P450 systems including cholesterol side chain cleavage in all steroidogenic tissues, steroid 11-beta hydroxylation in the adrenal cortex, 25-OH-vitamin D3-24 hydroxylation in the kidney, and sterol C-27 hydroxylation in the liver (By similarity). Also acts as a ferredoxin--NADP(+) reductase essential for coenzyme Q biosynthesis: together with FDX2, transfers the electrons required for the hydroxylation reaction performed by C

MitochondrionMitochondrion inner membrane

Auditory neuropathy and optic atrophy

An autosomal recessive disease characterized by hearing loss, visual impairment and optic atrophy, with onset in the first or second decades of life. Optic atrophy is caused by degeneration of nerve fibers which arise in the retina and converge to form the optic disk, optic nerve, optic chiasm and optic tracts.

Catalyzes the reduction of the C14-unsaturated bond of lanosterol, as part of the metabolic pathway leading to cholesterol biosynthesis (PubMed:12618959, PubMed:16784888, PubMed:21327084, PubMed:27336722, PubMed:9630650). Plays a critical role in myeloid cell cholesterol biosynthesis which is essential to both myeloid cell growth and functional maturation (By similarity). Mediates the activation of NADPH oxidases, perhaps by maintaining critical levels of cholesterol required for membrane lipid

Nucleus inner membraneEndoplasmic reticulum membraneCytoplasmNucleus

Pelger-Huet anomaly

An autosomal dominant inherited abnormality of granulocytes, characterized by abnormal ovoid shape, reduced nuclear segmentation and an apparently looser chromatin structure.

Endoplasmic reticulum (ER)-membrane-bound lysine N-acetyltransferase catalyzing the N6-acetylation of lysine residues in the lumen of the ER in various proteins, including PROM1 and BACE1, using acetyl-CoA as acetyl donor (PubMed:19011241, PubMed:22267734, PubMed:24556617, PubMed:31945187). Thereby, may regulate apoptosis through the acetylation and the regulation of the expression of PROM1 (PubMed:24556617). May also regulate amyloid beta-peptide secretion through acetylation of BACE1 and the r

Endoplasmic reticulum-Golgi intermediate compartment membraneEndoplasmic reticulum membrane

Protein insertase that mediates insertion of transmembrane proteins into the mitochondrial outer membrane (PubMed:36264797). Catalyzes insertion of proteins with alpha-helical transmembrane regions, such as signal-anchored, tail-anchored and multi-pass membrane proteins (By similarity). Does not mediate insertion of beta-barrel transmembrane proteins (By similarity). May play a role in apoptosis (PubMed:12377771)

Mitochondrion outer membrane

Plays a role in tight junctions and adherens junctions (By similarity). Acts as a positive regulator of RANKL-induced osteoclast differentiation, potentially via mediating downstream transcriptional activity (By similarity)

Cell junction, adherens junctionCell membraneCell junction, tight junctionNucleus

Hypercholanemia, familial, 1

A disorder characterized by elevated serum bile acid concentrations, itching, and fat malabsorption.

Involved in the fatty acid remodeling steps of GPI-anchor maturation where the unsaturated acyl chain at sn-2 of inositol phosphate is replaced by a saturated stearoyl chain (PubMed:17021251, PubMed:24439110). May catalyze the first step of the fatty acid remodeling, by removing the unsaturated acyl chain at sn-2 of inositol phosphate, generating a lyso-GPI intermediate (Probable). The fatty acid remodeling steps is critical for the integration of GPI-APs into lipid rafts (By similarity)

Golgi apparatus membrane

Hyperphosphatasia with impaired intellectual development syndrome 4

An autosomal recessive neurologic disorder characterized by profound developmental delay, severe intellectual disability, no speech, psychomotor delay, postnatal microcephaly, and elevated serum alkaline phosphatase.

Key enzyme in triglyceride metabolism. Catalyzes the hydrolysis of triglycerides from circulating chylomicrons and very low density lipoproteins (VLDL), and thereby plays an important role in lipid clearance from the blood stream, lipid utilization and storage (PubMed:11342582, PubMed:27578112, PubMed:8675619). Although it has both phospholipase and triglyceride lipase activities it is primarily a triglyceride lipase with low but detectable phospholipase activity (PubMed:12032167, PubMed:7592706

Cell membraneSecretedSecreted, extracellular space, extracellular matrix

Hyperlipoproteinemia 1

An autosomal recessive metabolic disorder characterized by defective breakdown of dietary fats, impaired clearance of chylomicrons from plasma causing the plasma to have a milky appearance, and severe hypertriglyceridemia. On a normal diet, patients often present with abdominal pain, hepatosplenomegaly, lipemia retinalis, eruptive xanthomata, and massive hypertriglyceridemia, sometimes complicated with acute pancreatitis.

Catalyzes the transport of triglyceride, cholesteryl ester, and phospholipid between phospholipid surfaces (PubMed:15897609, PubMed:16478722, PubMed:22236406, PubMed:23475612, PubMed:25108285, PubMed:26224785, PubMed:8876250, PubMed:8939939). Required for the assembly and secretion of plasma lipoproteins that contain apolipoprotein B (PubMed:16478722, PubMed:23475612, PubMed:26224785, PubMed:8876250, PubMed:8939939). May be involved in regulating cholesteryl ester biosynthesis in cells that prod

Endoplasmic reticulumGolgi apparatus

Abetalipoproteinemia

An autosomal recessive disorder of lipoprotein metabolism. Affected individuals produce virtually no circulating apolipoprotein B-containing lipoproteins (chylomicrons, VLDL, LDL, lipoprotein(A)). Malabsorption of the antioxidant vitamin E occurs, leading to spinocerebellar and retinal degeneration.

Receptor that mediates peroxisomal import of proteins containing a C-terminal PTS1-type tripeptide peroxisomal targeting signal (SKL-type) (PubMed:11101887, PubMed:11336669, PubMed:12456682, PubMed:16314507, PubMed:17157249, PubMed:17428317, PubMed:21976670, PubMed:26344566, PubMed:7706321, PubMed:7719337, PubMed:7790377). Binds to cargo proteins containing a PTS1 peroxisomal targeting signal in the cytosol, and translocates them into the peroxisome matrix by passing through the PEX13-PEX14 dock

Cytoplasm, cytosolPeroxisome matrix

Peroxisome biogenesis disorder 2A

A fatal peroxisome biogenesis disorder belonging to the Zellweger disease spectrum and characterized clinically by severe neurologic dysfunction with profound psychomotor retardation, severe hypotonia and neonatal seizures, craniofacial abnormalities, liver dysfunction, and biochemically by the absence of peroxisomes. Additional features include cardiovascular and skeletal defects, renal cysts, ocular abnormalities, and hearing impairment. Most severely affected individuals with the classic form of the disease (classic Zellweger syndrome) die within the first year of life.

Adapter protein (clathrin-associated sorting protein (CLASP)) required for efficient endocytosis of the LDL receptor (LDLR) in polarized cells such as hepatocytes and lymphocytes, but not in non-polarized cells (fibroblasts). May be required for LDL binding and internalization but not for receptor clustering in coated pits. May facilitate the endocytosis of LDLR and LDLR-LDL complexes from coated pits by stabilizing the interaction between the receptor and the structural components of the pits.

Cytoplasm

Hypercholesterolemia, familial, 4

A form of hypercholesterolemia, a disorder of lipoprotein metabolism characterized by elevated serum low-density lipoprotein (LDL) cholesterol levels, which result in excess deposition of cholesterol in tissues and leads to xanthelasma, xanthomas, accelerated atherosclerosis and increased risk of premature coronary heart disease. FHCL4 inheritance is autosomal recessive.

Converts testosterone (T) into 5-alpha-dihydrotestosterone (DHT) and progesterone or corticosterone into their corresponding 5-alpha-3-oxosteroids. It plays a central role in sexual differentiation and androgen physiology

Microsome membraneEndoplasmic reticulum membrane

Pseudovaginal perineoscrotal hypospadias

A form of male pseudohermaphroditism in which 46,XY males show ambiguous genitalia at birth, including perineal hypospadias and a blind perineal pouch, and develop masculinization at puberty. The name of the disorder stems from the finding of a blind-ending perineal opening resembling a vagina and a severely hypospadiac penis with the urethra opening onto the perineum.

A cytochrome P450 monooxygenase involved in the metabolism of endogenous oxysterols and steroid hormones, including neurosteroids (PubMed:10588945, PubMed:24491228). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) (PubMed:10588945, PubMed:24491228). Catalyzes the hydroxylation of carbon hydrogen bonds of stero

Endoplasmic reticulum membraneMicrosome membrane

Spastic paraplegia 5A, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Hydrolyzes the non-reducing end N-acetyl-D-hexosamine and/or sulfated N-acetyl-D-hexosamine of glycoconjugates, such as the oligosaccharide moieties from proteins and neutral glycolipids, or from certain mucopolysaccharides (PubMed:11707436, PubMed:8123671, PubMed:8672428, PubMed:9694901). The isozyme S is as active as the isozyme A on the anionic bis-sulfated glycans, the chondroitin-6-sulfate trisaccharide (C6S-3), and the dermatan sulfate pentasaccharide, and the sulfated glycosphingolipid SM

Lysosome

GM2-gangliosidosis 1

An autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. It is characterized by GM2 gangliosides accumulation in the absence of HEXA activity, leading to neurodegeneration and, in the infantile form, death in early childhood. It exists in several forms: infantile (most common and most severe), juvenile and adult (late-onset).

Heterodimeric electron transfer flavoprotein that accepts electrons from several mitochondrial dehydrogenases, including acyl-CoA dehydrogenases, glutaryl-CoA and sarcosine dehydrogenase (PubMed:15159392, PubMed:15975918, PubMed:25416781). It transfers the electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (Probable). Required for normal mitochondrial fatty acid oxidation and normal amino acid metabolism (PubMed:12815589, PubMed:7912128). ETFB binds an AMP mo

Mitochondrion matrix

Glutaric aciduria 2B

An autosomal recessively inherited disorder of fatty acid, amino acid, and choline metabolism. It is characterized by multiple acyl-CoA dehydrogenase deficiencies resulting in large excretion not only of glutaric acid, but also of lactic, ethylmalonic, butyric, isobutyric, 2-methyl-butyric, and isovaleric acids.

Catalyzes the hydrolysis of triglycerides and phospholipids present in circulating plasma lipoproteins, including chylomicrons, intermediate density lipoproteins (IDL), low density lipoproteins (LDL) of large size and high density lipoproteins (HDL), releasing free fatty acids (FFA) and smaller lipoprotein particles (PubMed:12032167, PubMed:26193433, PubMed:7592706, PubMed:8798474). Also exhibits lysophospholipase activity (By similarity). Can hydrolyze both neutral lipid and phospholipid substr

Secreted

Hepatic lipase deficiency

A disorder characterized by elevated levels of beta-migrating very low density lipoproteins, and abnormally triglyceride-rich low and high density lipoproteins.

Lipoyl amidotransferase that catalyzes the transfer of lipoyl moieties from lipoyl-protein H of the glycine cleavage system (lipoyl-GCSH) to E2 subunits of the pyruvate dehydrogenase complex (PDCE2) (PubMed:29987032). Unable to catalyze the transfer of octanoyl from octanoyl-GCSH to PDCE2 (PubMed:29987032). In vitro, it is also able to catalyze the transfer of the lipoyl group from lipoyl-AMP to the specific lysine residue of lipoyl domains of lipoate-dependent enzymes but this reaction may not

Mitochondrion

Lipoyltransferase 1 deficiency

An autosomal recessive disorder due to a defect in lipoic acid metabolism, resulting in severe lactic acidosis and metabolic decompensation. Variable clinical manifestations include delayed psychomotor development, severe hypotonia, dystonia, loss of head control, coma, bradycardia, and pulmonary hypertension.

Binds low density lipoprotein /LDL, the major cholesterol-carrying lipoprotein of plasma, and transports it into cells by endocytosis. In order to be internalized, the receptor-ligand complexes must first cluster into clathrin-coated pits. Forms a ternary complex with PGRMC1 and TMEM97 receptors which increases LDLR-mediated LDL internalization (PubMed:30443021) (Microbial infection) Acts as a receptor for hepatitis C virus in hepatocytes, but not through a direct interaction with viral proteins

Cell membraneMembrane, clathrin-coated pitGolgi apparatusEarly endosomeLate endosomeLysosome

Hypercholesterolemia, familial, 1

A form of hypercholesterolemia, a disorder of lipoprotein metabolism characterized by elevated serum low-density lipoprotein (LDL) cholesterol levels, which result in excess deposition of cholesterol in tissues and leads to xanthelasma, xanthomas, accelerated atherosclerosis and increased risk of premature coronary heart disease. FHCL1 inheritance is autosomal dominant.

Catalyzes the penultimate step of the biosynthesis of cholesterol, the dehydrogenation of lathosterol into 7-dehydrocholesterol (7-DHC). Cholesterol is the major sterol component in mammalian membranes and a precursor for bile acid and steroid hormone synthesis (PubMed:10786622, PubMed:38297129). In addition to its essential role in cholesterol biosynthesis, it also indirectly regulates ferroptosis through the production of 7-DHC. By diverting the spread of damage caused by peroxyl radicals from

Endoplasmic reticulum membrane

Lathosterolosis

An autosomal recessive disorder characterized by multiple congenital anomalies affecting axial and appendicular skeleton, liver, central nervous and urogenital systems, and lysosomal storage.

Acts as a lysosomal receptor for glucosylceramidase (GBA1) targeting (Microbial infection) Acts as a receptor for enterovirus 71

Lysosome membrane

Epilepsy, progressive myoclonic 4, with or without renal failure

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM4 is an autosomal recessive form associated with renal failure in some cases. Cognitive function is preserved.

Glucosylceramidase that catalyzes, within the lysosomal compartment, the hydrolysis of glucosylceramides/GlcCers (such as beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine) into free ceramides (such as N-acylsphing-4-enine) and glucose (PubMed:15916907, PubMed:24211208, PubMed:32144204, PubMed:39395789, PubMed:9201993). Plays a central role in the degradation of complex lipids and the turnover of cellular membranes (PubMed:27378698). Through the production of ceramides, participates in the PKC-activ

Lysosome membrane

Gaucher disease

An autosomal recessive lysosomal storage disease due to deficient activity of lysosomal beta-glucocerebrosidase, and characterized by accumulation of glucosylceramide in the reticulo-endothelial system. GD is a multisystem disease historically divided into three main subtypes on the basis of the presence of neurologic involvement, age at onset and progression rate: type 1 is the non-neuropathic form, type 2 is the acute neuropathic form with early onset and rapid neurologic deterioration, type 3 is the chronic neuropathic form with slow progression of neurologic features. GD shows a marked phenotypic diversity ranging from adult asymptomatic forms, at the mild end, to perinatal lethal forms at the severe end of the disease spectrum. Formal diagnosis of Gaucher disease is based on the measurement of glucocerebrosidase levels in circulating leukocytes and molecular genetic analysis.

Catalytic subunit of the glycosylphosphatidylinositol-anchor (GPI-anchor) transamidase (GPI-T) complex that catalyzes the formation of the linkage between a proprotein and a GPI-anchor and participates in GPI anchored protein biosynthesis (PubMed:10793132, PubMed:11483512, PubMed:12582175, PubMed:34576938, PubMed:35165458, PubMed:35551457, PubMed:37684232, PubMed:9356492). Recognizes diverse proproteins at a C-terminal signal peptide (CSP) region that lacks consensus sequence and replaces it wit

Endoplasmic reticulum membrane

Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures

An autosomal recessive neurodevelopmental disorder characterized by global developmental delay, intellectual disability, hypotonia, cerebellar ataxia, cerebellar atrophy, delayed motor skills, poor or absent speech, and epilepsy in most patients. Some patients manifest facial dysmorphism. Disease onset is in infancy.

Catalytic subunit of the essential mitochondrial processing protease (MPP), which cleaves the mitochondrial sequence off newly imported precursors proteins (Probable) (PubMed:29576218). Preferentially, cleaves after an arginine at position P2 (By similarity). Required for PINK1 turnover by coupling PINK1 mitochondrial import and cleavage, which results in subsequent PINK1 proteolysis (PubMed:22354088)

Mitochondrion matrix

Multiple mitochondrial dysfunctions syndrome 6

An autosomal recessive, neurodegenerative disorder characterized by basal ganglia lesions, cerebellar atrophy, and neurologic regression in the first year of life. Common features include truncal hypotonia, lack of independent ambulation, poor speech, intellectual disability, and motor abnormalities, such as ataxia, dystonia, and spasticity.

Component of the glycosylphosphatidylinositol-anchor (GPI-anchor) transamidase (GPI-T) complex that catalyzes the formation of the linkage between a proprotein and a GPI-anchor and participates in GPI anchored protein biosynthesis (PubMed:11483512, PubMed:12582175, PubMed:28327575, PubMed:34576938, PubMed:35165458, PubMed:35551457, PubMed:36970549, PubMed:37684232). May play a crucial role in GPI-T complex assembly in the luminal layer (PubMed:35165458, PubMed:35551457). Binds GPI-anchor (PubMed

Endoplasmic reticulum membrane

Multiple congenital anomalies-hypotonia-seizures syndrome 3

An autosomal recessive syndrome characterized by distinct facial features, intellectual disability, hypotonia and seizures, in combination with abnormal skeletal, endocrine, and ophthalmologic findings including impaired vision, as well as abnormal motility of the eyes.

Catalyzes the deacylation of cholesteryl ester core lipids of endocytosed low density lipoproteins to generate free fatty acids and cholesterol (PubMed:15269241, PubMed:1718995, PubMed:7204383, PubMed:8112342, PubMed:9633819). Hydrolyzes triglycerides (1,2,3-triacylglycerol) and diglycerides (such as 1,2-diacylglycerol and 1,3-diacylglycerol) with preference for the acyl moieties at the sn-1 or sn-3 positions (PubMed:7204383, PubMed:8112342)

Lysosome

Cholesteryl ester storage disease

An autosomal recessive, mild form of lysosomal acid lipase deficiency characterized by accumulation of cholesteryl esters and triglycerides primarily in the liver. The clinical presentation is highly variable depending on residual levels of lysosomal acid lipase activity, and ranges from early onset of severe cirrhosis to later onset of more slowly progressive hepatic disease with survival into adulthood. Age at onset varies from childhood to adulthood.

Catalyzes the three-step monooxygenation required for the demethylation of 4,4-dimethyl and 4alpha-methylsterols, which can be subsequently metabolized to cholesterol (PubMed:21285510, PubMed:23583456, PubMed:26114596, PubMed:28673550, PubMed:36958722). Also involved in drug metabolism, as it can metabolize eldecalcitol (ED-71 or 1alpha,25-dihydroxy-2beta-(3-hydroxypropoxy)-cholecalciferol), a second-generation vitamin D analog, into 1alpha,2beta,25-trihydroxy vitamin D3; this reaction occurs vi

Endoplasmic reticulum membrane

Microcephaly, congenital cataract, and psoriasiform dermatitis

An autosomal recessive inborn error of cholesterol metabolism characterized by accumulation of a large amount of methylsterols, particularly dimethylsterols, in affected individuals. Patients manifest psoriasiform dermatitis, arthralgias, congenital cataracts, microcephaly, and developmental delay.

Involved in the maturation of mitochondrial 4Fe-4S proteins functioning late in the iron-sulfur cluster assembly pathway. May be involved in the binding of an intermediate of Fe/S cluster assembly

Mitochondrion

Multiple mitochondrial dysfunctions syndrome 4

A severe disorder of systemic energy metabolism, resulting in weakness, respiratory failure, lack of neurologic development, lactic acidosis, hyperglycinemia and early death.

As a major transporter of conjugated bile salts from plasma into the hepatocyte, it plays a key role in the enterohepatic circulation of bile salts necessary for the solubilization and absorption of dietary fat and fat-soluble vitamins (PubMed:14660639, PubMed:24867799, PubMed:34060352, PubMed:8132774). It is strictly dependent on the extracellular presence of sodium (PubMed:14660639, PubMed:24867799, PubMed:34060352, PubMed:8132774). It exhibits broad substrate specificity and transports variou

Cell membrane

Hypercholanemia, familial, 2

An autosomal recessive inborn error of metabolism characterized by persistently increased plasma levels of conjugated bile salts apparent from infancy, fat malabsorption and impaired absorption of fat-soluble vitamins, including D and K. Most patients are asymptomatic. Some neonates may have transient jaundice or transiently elevated liver enzymes.

Central enzyme in the extracellular metabolism of plasma lipoproteins. Synthesized mainly in the liver and secreted into plasma where it converts cholesterol and phosphatidylcholines (lecithins) to cholesteryl esters and lysophosphatidylcholines on the surface of high and low density lipoproteins (HDLs and LDLs) (PubMed:10329423, PubMed:19065001, PubMed:26195816). The cholesterol ester is then transported back to the liver. Has a preference for plasma 16:0-18:2 or 18:O-18:2 phosphatidylcholines

Secreted

Lecithin-cholesterol acyltransferase deficiency

A disorder of lipoprotein metabolism characterized by inadequate esterification of plasmatic cholesterol. Two clinical forms are recognized: complete LCAT deficiency and fish-eye disease. LCATD is generally referred to the complete form which is associated with absence of both alpha and beta LCAT activities resulting in esterification anomalies involving both HDL (alpha-LCAT activity) and LDL (beta-LCAT activity). It causes a typical triad of diffuse corneal opacities, target cell hemolytic anemia, and proteinuria with renal failure.

Mitochondrial trifunctional enzyme catalyzes the last three of the four reactions of the mitochondrial beta-oxidation pathway (PubMed:1550553, PubMed:29915090, PubMed:30850536, PubMed:8135828, PubMed:31604922). The mitochondrial beta-oxidation pathway is the major energy-producing process in tissues and is performed through four consecutive reactions breaking down fatty acids into acetyl-CoA (PubMed:29915090). Among the enzymes involved in this pathway, the trifunctional enzyme exhibits specific

MitochondrionMitochondrion inner membrane

Mitochondrial trifunctional protein deficiency 1

An autosomal recessive metabolic disorder of long-chain fatty acid oxidation, biochemically characterized by loss of all enzyme activities of the mitochondrial trifunctional protein complex. The disease phenotype ranges from a fatal form characterized by early-onset cardiomyopathy, cardiac failure and early death to less severe, late-onset forms with myopathy, recurrent rhabdomyolysis, and sensorimotor axonal neuropathy as key features.

Catalyzes the second step of glycosylphosphatidylinositol (GPI) biosynthesis, which is the de-N-acetylation of N-acetylglucosaminyl-phosphatidylinositol

Endoplasmic reticulum membrane

Coloboma, congenital heart disease, ichthyosiform dermatosis, impaired intellectual development, and ear anomalies syndrome

An extremely rare autosomal recessive multisystem disorder clinically characterized by colobomas, congenital heart defects, migratory ichthyosiform dermatosis, intellectual disability, and ear anomalies including conductive hearing loss. Other clinical features include distinctive facial features, abnormal growth, genitourinary abnormalities, seizures, and feeding difficulties.

Oxidoreductase that catalyzes the last step of the cholesterol synthesis pathway, which transforms cholesta-5,7-dien-3beta-ol (7-dehydrocholesterol,7-DHC) into cholesterol by reducing the C7-C8 double bond of its sterol core (PubMed:25637936, PubMed:38297129, PubMed:38297130, PubMed:9465114, PubMed:9634533). Can also metabolize cholesta-5,7,24-trien-3beta-ol (7-dehydrodemosterol, 7-DHD) to desmosterol, which is then metabolized by the Delta(24)-sterol reductase (DHCR24) to cholesterol (By simila

Endoplasmic reticulum membrane

Smith-Lemli-Opitz syndrome

An autosomal recessive frequent inborn disorder of sterol metabolism with characteristic congenital malformations and intellectual disability. Children with SLOS have elevated serum 7-dehydrocholesterol (7-DHC) levels and low serum cholesterol levels. SLOS occurs in relatively high frequency: approximately 1 in 20,000 to 30,000 births in populations of northern and central European background. Historically, a clinical distinction often was made between classic ('type I') SLOS and the more severely affected ('type II') patients. There is, in reality, a clinical and biochemical continuum from mild to severe SLOS.

Mitochondrial NAD(+) kinase that phosphorylates NAD(+) to yield NADP(+). Can use both ATP or inorganic polyphosphate as the phosphoryl donor. Also has weak NADH kinase activity in vitro; however NADH kinase activity is much weaker than the NAD(+) kinase activity and may not be relevant in vivo

Mitochondrion

2,4-dienoyl-CoA reductase deficiency

A rare, autosomal recessive, inborn error of polyunsaturated fatty acids and lysine metabolism, resulting in mitochondrial dysfunction. Affected individuals have a severe encephalopathy with neurologic and metabolic abnormalities beginning in early infancy. Laboratory studies show increased C10:2 carnitine levels and hyperlysinemia.

Tyrosine-protein kinase that acts as a cell-surface receptor for fibroblast growth factors and plays an essential role in the regulation of embryonic development, cell proliferation, differentiation and migration. Required for normal mesoderm patterning and correct axial organization during embryonic development, normal skeletogenesis and normal development of the gonadotropin-releasing hormone (GnRH) neuronal system. Phosphorylates PLCG1, FRS2, GAB1 and SHB. Ligand binding leads to the activati

Cell membraneNucleusCytoplasm, cytosolCytoplasmic vesicle

Pfeiffer syndrome

A syndrome characterized by the association of craniosynostosis, broad and deviated thumbs and big toes, and partial syndactyly of the fingers and toes. Three subtypes are known: mild autosomal dominant form (type 1); cloverleaf skull, elbow ankylosis, early death, sporadic (type 2); craniosynostosis, early demise, sporadic (type 3).

Monothiol glutaredoxin involved in mitochondrial iron-sulfur (Fe/S) cluster transfer (PubMed:20364084, PubMed:23615440). Receives 2Fe/2S clusters from scaffold protein ISCU and mediates their transfer to apoproteins, to the 4Fe/FS cluster biosynthesis machinery, or export from mitochondrion (PubMed:20364084, PubMed:23615440, PubMed:24334290). Required for normal regulation of hemoglobin synthesis by the iron-sulfur protein ACO1 (PubMed:20364084)

Mitochondrion matrix

Anemia, sideroblastic, 3, pyridoxine-refractory

A form of sideroblastic anemia, a bone marrow disorder defined by the presence of pathologic iron deposits in erythroblast mitochondria. Sideroblastic anemia is characterized by anemia of varying severity, hypochromic peripheral erythrocytes, systemic iron overload secondary to chronic ineffective erythropoiesis, and the presence of bone marrow ringed sideroblasts. Sideroblasts are characterized by iron-loaded mitochondria clustered around the nucleus. SIDBA3 is refractory to treatment with vitamin B6, while iron chelation therapy may result in clinical improvement. SIDBA3 inheritance is autosomal recessive.

Component of the serine palmitoyltransferase multisubunit enzyme (SPT) that catalyzes the initial and rate-limiting step in sphingolipid biosynthesis by condensing L-serine and activated acyl-CoA (most commonly palmitoyl-CoA) to form long-chain bases (PubMed:19416851, PubMed:19648650, PubMed:20504773, PubMed:20920666). The SPT complex is composed of SPTLC1, SPTLC2 or SPTLC3 and SPTSSA or SPTSSB. Within this complex, the heterodimer consisting of SPTLC1 and SPTLC2/SPTLC3 forms the catalytic core

Endoplasmic reticulum membrane

Neuropathy, hereditary sensory and autonomic, 1C

A form of hereditary sensory and autonomic neuropathy, a genetically and clinically heterogeneous group of disorders characterized by degeneration of dorsal root and autonomic ganglion cells, and by prominent sensory abnormalities with a variable degree of motor and autonomic dysfunction. The neurological phenotype is often complicated by severe infections, osteomyelitis, and amputations. HSAN1C symptoms include loss of touch and vibration in the feet, dysesthesia and severe panmodal sensory loss in the upper and lower limbs, distal lower limb sensory loss with ulceration and osteomyelitis, and distal muscle weakness.

Lipoamide dehydrogenase is a component of the glycine cleavage system as well as an E3 component of three alpha-ketoacid dehydrogenase complexes (pyruvate-, alpha-ketoglutarate-, and branched-chain amino acid-dehydrogenase complex) (PubMed:15712224, PubMed:16442803, PubMed:16770810, PubMed:17404228, PubMed:20160912, PubMed:20385101). The 2-oxoglutarate dehydrogenase complex is mainly active in the mitochondrion (PubMed:29211711). A fraction of the 2-oxoglutarate dehydrogenase complex also locali

Mitochondrion matrixNucleusCell projection, cilium, flagellumCytoplasmic vesicle, secretory vesicle, acrosome

Dihydrolipoamide dehydrogenase deficiency

An autosomal recessive metabolic disorder characterized biochemically by a combined deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), pyruvate dehydrogenase complex (PDC), and alpha-ketoglutarate dehydrogenase complex (KGDC). Clinically, affected individuals have lactic acidosis and neurologic deterioration due to sensitivity of the central nervous system to defects in oxidative metabolism.

Catalyzes the first irreversible step in ketogenesis, condensing acetyl-CoA to acetoacetyl-CoA to form HMG-CoA, which is converted by HMG-CoA reductase (HMGCR) into mevalonate

Mitochondrion

3-hydroxy-3-methylglutaryl-CoA synthase-2 deficiency

A metabolic disorder characterized by severe hypoketotic hypoglycemia, encephalopathy, and hepatomegaly.

Mitochondrial isoform that catalyzes the phosphorylation of pantothenate to generate 4'-phosphopantothenate in the first and rate-determining step of coenzyme A (CoA) synthesis (PubMed:15659606, PubMed:16272150, PubMed:17242360, PubMed:17825826). Required for angiogenic activity of umbilical vein of endothelial cells (HUVEC) (PubMed:30221726) Cytoplasmic isoform that catalyzes the phosphorylation of pantothenate to generate 4'-phosphopantothenate in the first and rate-determining step of coenzym

MitochondrionMitochondrion intermembrane spaceNucleusCytoplasm

Neurodegeneration with brain iron accumulation 1

Autosomal recessive neurodegenerative disorder associated with iron accumulation in the brain, primarily in the basal ganglia. Clinical manifestations include progressive muscle spasticity, hyperreflexia, muscle rigidity, dystonia, dysarthria, and intellectual deterioration which progresses to severe dementia over several years. It is clinically classified into classic, atypical, and intermediate phenotypes. Classic forms present with onset in first decade, rapid progression, loss of independent ambulation within 15 years. Atypical forms have onset in second decade, slow progression, maintenance of independent ambulation up to 40 years later. Intermediate forms manifest onset in first decade with slow progression or onset in second decade with rapid progression. Patients with early onset tend to also develop pigmentary retinopathy, whereas those with later onset tend to also have speech disorders and psychiatric features. All patients have the 'eye of the tiger' sign on brain MRI.

Hydrolyzes the non-reducing end N-acetyl-D-hexosamine and/or sulfated N-acetyl-D-hexosamine of glycoconjugates, such as the oligosaccharide moieties from proteins and neutral glycolipids, or from certain mucopolysaccharides (PubMed:11707436, PubMed:8123671, PubMed:8672428, PubMed:9694901). The isozyme B does not hydrolyze each of these substrates, however hydrolyzes efficiently neutral oligosaccharide (PubMed:11707436). Only the isozyme A is responsible for the degradation of GM2 gangliosides in

LysosomeCytoplasmic vesicle, secretory vesicle, Cortical granule

GM2-gangliosidosis 2

An autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. Clinically indistinguishable from GM2-gangliosidosis type 1, presenting startle reactions, early blindness, progressive motor and mental deterioration, macrocephaly and cherry-red spots on the macula.

Converts sphingomyelin to ceramide (PubMed:12563314, PubMed:1840600, PubMed:18815062, PubMed:25339683, PubMed:25920558, PubMed:27659707, PubMed:33163980). Exists as two enzymatic forms that arise from alternative trafficking of a single protein precursor, one that is targeted to the endolysosomal compartment, whereas the other is released extracellularly (PubMed:20807762, PubMed:21098024, PubMed:9660788). However, in response to various forms of stress, lysosomal exocytosis may represent a major

LysosomeLipid dropletSecretedSecreted, extracellular space

Niemann-Pick disease A

An early-onset lysosomal storage disorder caused by failure to hydrolyze sphingomyelin to ceramide. It results in the accumulation of sphingomyelin and other metabolically related lipids in reticuloendothelial and other cell types throughout the body, leading to cell death. Niemann-Pick disease type A is a primarily neurodegenerative disorder characterized by onset within the first year of life, intellectual disability, digestive disorders, failure to thrive, major hepatosplenomegaly, and severe neurologic symptoms. The severe neurological disorders and pulmonary infections lead to an early death, often around the age of four. Clinical features are variable. A phenotypic continuum exists between type A (basic neurovisceral) and type B (purely visceral) forms of Niemann-Pick disease, and the intermediate types encompass a cluster of variants combining clinical features of both types A and B.

Catalyzes the NADPH-dependent reduction of trans-2-enoyl thioesters in mitochondrial fatty acid synthesis (fatty acid synthesis type II). Fatty acid chain elongation in mitochondria uses acyl carrier protein (ACP) as an acyl group carrier, but the enzyme accepts both ACP and CoA thioesters as substrates in vitro. Displays a preference for medium-chain over short- and long-chain substrates (PubMed:12654921, PubMed:18479707, PubMed:27817865). May provide the octanoyl chain used for lipoic acid bio

MitochondrionCytoplasmNucleus

Dystonia, childhood-onset, with optic atrophy and basal ganglia abnormalities

An autosomal recessive neurologic disorder characterized by childhood-onset dystonia, basal ganglia degeneration and optic atrophy with decreased visual acuity. Dystonia is defined by the presence of sustained involuntary muscle contraction, often leading to abnormal postures. DYTOABG severity is variable, and some patients lose independent ambulation.

The large binding pocket can accommodate several single chain phospholipids and fatty acids, GM2A also exhibits some calcium-independent phospholipase activity (By similarity). Binds gangliosides and stimulates ganglioside GM2 degradation. It stimulates only the breakdown of ganglioside GM2 and glycolipid GA2 by beta-hexosaminidase A. It extracts single GM2 molecules from membranes and presents them in soluble form to beta-hexosaminidase A for cleavage of N-acetyl-D-galactosamine and conversion

Lysosome

GM2-gangliosidosis AB

An autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. It is characterized by GM2 gangliosides accumulation in the presence of both normal hexosaminidase A and B.

Part of the glycosylphosphatidylinositol-N-acetylglucosaminyltransferase (GPI-GnT) complex that catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to phosphatidylinositol and participates in the first step of GPI biosynthesis (PubMed:16162815). May act by regulating the catalytic subunit PIGA (PubMed:16162815)

Endoplasmic reticulum membrane

Hyperphosphatasia with impaired intellectual development syndrome 6

An autosomal recessive, multisystem disorder characterized by severe developmental delay, dysmorphism, seizures, cataracts, and early death in some patients.

May be involved in the control of excitability of cortical neurons

Cell membraneCytoplasm, cytosol

Epilepsy, progressive myoclonic 3, with or without intracellular inclusions

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM3 is an autosomal recessive, severe, form with early onset. Multifocal myoclonic seizures begin between 16 and 24 months of age after normal initial development. Neurodegeneration and regression occur with seizure onset. Other features include intellectual disability, dysarthria, truncal ataxia, and loss of fine finger movements. EEG shows slow dysrhythmia, multifocal and occasionally generalized epileptiform discharges. In some patients, ultrastructural findings on skin biopsies identify intracellular accumulation of autofluorescent lipopigment storage material, consistent with neuronal ceroid lipofuscinosis.

Mitochondrial trifunctional enzyme catalyzes the last three of the four reactions of the mitochondrial beta-oxidation pathway (PubMed:29915090, PubMed:30850536, PubMed:8135828). The mitochondrial beta-oxidation pathway is the major energy-producing process in tissues and is performed through four consecutive reactions breaking down fatty acids into acetyl-CoA (PubMed:29915090). Among the enzymes involved in this pathway, the trifunctional enzyme exhibits specificity for long-chain fatty acids (P

MitochondrionMitochondrion inner membraneMitochondrion outer membraneEndoplasmic reticulum

Mitochondrial trifunctional protein deficiency 2

An autosomal recessive metabolic disorder of long-chain fatty acid oxidation, biochemically characterized by loss of all enzyme activities of the mitochondrial trifunctional protein complex. The disease phenotype ranges from a fatal form characterized by early-onset cardiomyopathy, cardiac failure and early death to less severe, late-onset forms with myopathy, recurrent rhabdomyolysis, and sensorimotor axonal neuropathy as key features.

Heterodimeric electron transfer flavoprotein that accepts electrons from several mitochondrial dehydrogenases, including acyl-CoA dehydrogenases, glutaryl-CoA and sarcosine dehydrogenase (PubMed:10356313, PubMed:15159392, PubMed:15975918, PubMed:27499296, PubMed:9334218). It transfers the electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase) (PubMed:9334218). Required for normal mitochondrial fatty acid oxidation and normal amino acid metabol

Mitochondrion matrix

Glutaric aciduria 2A

An autosomal recessively inherited disorder of fatty acid, amino acid, and choline metabolism. It is characterized by multiple acyl-CoA dehydrogenase deficiencies resulting in large excretion not only of glutaric acid, but also of lactic, ethylmalonic, butyric, isobutyric, 2-methyl-butyric, and isovaleric acids.

Intracellular cholesterol transporter which acts in concert with NPC2 and plays an important role in the egress of cholesterol from the endosomal/lysosomal compartment (PubMed:10821832, PubMed:12554680, PubMed:18772377, PubMed:27238017, PubMed:9211849, PubMed:9927649). Unesterified cholesterol that has been released from LDLs in the lumen of the late endosomes/lysosomes is transferred by NPC2 to the cholesterol-binding pocket in the N-terminal domain of NPC1 (PubMed:18772377, PubMed:19563754, Pu

Late endosome membraneLysosome membrane

Niemann-Pick disease C1

A lysosomal storage disorder that affects the viscera and the central nervous system. It is due to defective intracellular processing and transport of low-density lipoprotein derived cholesterol. It causes accumulation of cholesterol in lysosomes, with delayed induction of cholesterol homeostatic reactions. Niemann-Pick disease type C1 has a highly variable clinical phenotype. Clinical features include variable hepatosplenomegaly and severe progressive neurological dysfunction such as ataxia, dystonia and dementia. The age of onset can vary from infancy to late adulthood. An allelic variant of Niemann-Pick disease type C1 is found in people with Nova Scotia ancestry. Patients with the Nova Scotian clinical variant are less severely affected.

Phospholipase B that deacylates intracellular phosphatidylcholine (PtdCho), generating glycerophosphocholine (GroPtdCho). This deacylation occurs at both sn-2 and sn-1 positions of PtdCho. Catalyzes the hydrolysis of several naturally occurring membrane-associated lipids (PubMed:11927584). Hydrolyzes lysophospholipids and monoacylglycerols, preferring the 1-acyl to the 2-acyl isomer. Does not catalyze hydrolysis of di- or triacylglycerols or fatty acid amides (PubMed:11927584)

Endoplasmic reticulum membrane

Spastic paraplegia 39, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. SPG39 is associated with a motor axonopathy affecting upper and lower limbs and resulting in progressive wasting of distal upper and lower extremity muscles.

Oxidase that catalyzes the conversion of cysteine to 3-oxoalanine on target proteins, using molecular oxygen and an unidentified reducing agent (PubMed:12757706, PubMed:15657036, PubMed:15907468, PubMed:16368756, PubMed:21224894, PubMed:25931126). 3-oxoalanine modification, which is also named formylglycine (fGly), occurs in the maturation of arylsulfatases and some alkaline phosphatases that use the hydrated form of 3-oxoalanine as a catalytic nucleophile (PubMed:12757706, PubMed:15657036, PubM

Endoplasmic reticulum lumen

Multiple sulfatase deficiency

A clinically and biochemically heterogeneous disorder caused by the simultaneous impairment of all sulfatases, due to defective post-translational modification and activation. It combines features of individual sulfatase deficiencies such as metachromatic leukodystrophy, mucopolysaccharidosis, chondrodysplasia punctata, hydrocephalus, ichthyosis, neurologic deterioration and developmental delay.

Catalyzes the conversion of sulfated steroid precursors, such as dehydroepiandrosterone sulfate (DHEA-S) and estrone sulfate to the free steroid

Cytoplasmic vesicle, secretory vesicle, microneme membraneEndoplasmic reticulum membrane

Ichthyosis, X-linked

A keratinization disorder manifesting with mild erythroderma and generalized exfoliation of the skin within a few weeks after birth. Affected boys later develop large, polygonal, dark brown scales, especially on the neck, extremities, trunk, and buttocks.

Secreted protein that acts as a key regulator of lysosomal function and as a growth factor involved in inflammation, wound healing and cell proliferation (PubMed:12526812, PubMed:18378771, PubMed:28073925, PubMed:28453791, PubMed:28541286). Regulates protein trafficking to lysosomes, and also the activity of lysosomal enzymes (PubMed:28453791, PubMed:28541286). Also facilitates the acidification of lysosomes, causing degradation of mature CTSD by CTSB (PubMed:28073925). In addition, functions as

SecretedLysosome

Frontotemporal dementia 2

A form of dementia characterized by pathologic finding of frontotemporal lobar degeneration, presenile dementia with behavioral changes, deterioration of cognitive capacities and loss of memory. Gestural apraxia, parkinsonism, visual loss, and visual hallucinations are present in 25 to 40% of patients.

Has a key role in phospholipid metabolism, and catalyzes the first step of phosphatidylethanolamine and phosphatidylcholine biosynthesis

Muscular dystrophy, congenital, megaconial type

An autosomal recessive, congenital muscular dystrophy characterized by early-onset muscle wasting, intellectual disability, and dilated cardiomyopathy in half of affected individuals. Some patients may die from cardiomyopathy in the first or second decade of life. Muscle biopsy shows peculiar enlarged mitochondria that are prevalent toward the periphery of the fibers but are sparse in the center.

Exhibits arylsulfatase activity towards the artificial substrate 4-methylumbelliferyl sulfate (PubMed:7720070, PubMed:9497243). May be essential for the correct composition of cartilage and bone matrix during development (PubMed:7720070). Has no activity toward steroid sulfates (PubMed:7720070)

Golgi apparatus, Golgi stack

Chondrodysplasia punctata 1, X-linked recessive

A clinically and genetically heterogeneous disorder characterized by punctiform calcification of the bones. CDPX1 is a congenital defect of bone and cartilage development characterized by aberrant bone mineralization, severe underdevelopment of nasal cartilage, and distal phalangeal hypoplasia. This disease can also be induced by inhibition with the drug warfarin.

Catalyzes the interconversion of (R)- and (S)-stereoisomers of alpha-methyl-branched-chain fatty acyl-CoA esters (PubMed:10655068, PubMed:11060359, PubMed:7649182). Acts only on coenzyme A thioesters, not on free fatty acids, and accepts as substrates a wide range of alpha-methylacyl-CoAs, including pristanoyl-CoA, trihydroxycoprostanoyl-CoA (an intermediate in bile acid synthesis), and arylpropionic acids like the anti-inflammatory drug ibuprofen (2-(4-isobutylphenyl)propionic acid) but neither

PeroxisomeMitochondrion

Alpha-methylacyl-CoA racemase deficiency

A rare autosomal recessive peroxisomal disorder characterized by elevated plasma concentrations of pristanic acid C27-bile-acid intermediates, and adult onset of variable neurodegenerative symptoms affecting the central and peripheral nervous systems. Features may include seizures, visual failure, sensorimotor neuropathy, spasticity, migraine, and white matter hyperintensities on brain imaging.

Catalyzes the translocation of specific phospholipids from the cytoplasmic to the extracellular/lumenal leaflet of membrane coupled to the hydrolysis of ATP (PubMed:24097981, PubMed:35974019). Thereby, participates in phospholipid transfer to apolipoproteins to form nascent high density lipoproteins/HDLs (PubMed:14754908). Transports preferentially phosphatidylcholine over phosphatidylserine (PubMed:24097981). May play a similar role in the efflux of intracellular cholesterol to apolipoproteins

Cell membraneEndosome

Tangier disease

An autosomal recessive disorder characterized by near absence of plasma high density lipoproteins, low serum HDL cholesterol, and massive tissue deposition of cholesterol esters. Clinical features include large yellow-orange tonsils, hepatomegaly, splenomegaly, enlarged lymph nodes, and often sensory polyneuropathy.

Catalyzes the stereospecific NADPH-dependent reduction of the C4-C5 double bond of bile acid intermediates and steroid hormones carrying a delta(4)-3-one structure to yield an A/B cis-ring junction. This cis-configuration is crucial for bile acid biosynthesis and plays important roles in steroid metabolism. Capable of reducing a broad range of delta-(4)-3-ketosteroids from C18 (such as, 17beta-hydroxyestr-4-en-3-one) to C27 (such as, 7alpha-hydroxycholest-4-en-3-one)

Cytoplasm

Congenital bile acid synthesis defect 2

A condition characterized by jaundice, intrahepatic cholestasis and hepatic failure. Patients with this liver disease show absence or low levels of chenodeoxycholic acid and cholic acid in plasma and urine.

Catalyzes the formation of fatty acid-cholesterol esters, which are less soluble in membranes than cholesterol (PubMed:16154994, PubMed:16647063, PubMed:32433613, PubMed:32433614, PubMed:32944968, PubMed:9020103). Plays a role in lipoprotein assembly and dietary cholesterol absorption (PubMed:16154994, PubMed:9020103). Preferentially utilizes oleoyl-CoA ((9Z)-octadecenoyl-CoA) as a substrate: shows a higher activity towards an acyl-CoA substrate with a double bond at the delta-9 position (9Z) th

Endoplasmic reticulum membrane

Apolipoprotein B is a major protein constituent of chylomicrons (apo B-48), LDL (apo B-100) and VLDL (apo B-100). Apo B-100 functions as a recognition signal for the cellular binding and internalization of LDL particles by the apoB/E receptor

CytoplasmSecretedLipid droplet

Hypobetalipoproteinemia, familial, 1

A disorder of lipid metabolism characterized by less than 5th percentile age- and sex-specific levels of low density lipoproteins, and dietary fat malabsorption. Clinical presentation may vary from no symptoms to severe gastrointestinal and neurological dysfunction similar to abetalipoproteinemia.

Minor apolipoprotein mainly associated with HDL and to a lesser extent with VLDL. May also be associated with chylomicrons. Important determinant of plasma triglyceride (TG) levels by both being a potent stimulator of apo-CII lipoprotein lipase (LPL) TG hydrolysis and an inhibitor of the hepatic VLDL-TG production rate (without affecting the VLDL-apoB production rate) (By similarity). Activates poorly lecithin:cholesterol acyltransferase (LCAT) and does not enhance efflux of cholesterol from mac

SecretedEarly endosomeLate endosomeGolgi apparatus, trans-Golgi network

Hypertriglyceridemia 1

A common inherited disorder in which the concentration of very low density lipoprotein (VLDL) is elevated in the plasma. This leads to increased risk of heart disease, obesity, and pancreatitis. Inheritance is autosomal dominant.

Very long-chain specific acyl-CoA dehydrogenase is one of the acyl-CoA dehydrogenases that catalyze the first step of mitochondrial fatty acid beta-oxidation (FAO), breaking down fatty acids into acetyl-CoA and allowing the production of energy from fats (PubMed:17564966, PubMed:18227065, PubMed:7668252, PubMed:9461620, PubMed:9599005, PubMed:9839948). The first step of FAO consists in the proR-proR stereospecific alpha, beta-dehydrogenation of fatty acyl-CoA thioesters using the electron transf

Mitochondrion inner membrane

Acyl-CoA dehydrogenase very long-chain deficiency

An inborn error of mitochondrial fatty acid beta-oxidation which leads to impaired long-chain fatty acid beta-oxidation. It is clinically heterogeneous, with three major phenotypes: a severe childhood form characterized by early onset, high mortality and high incidence of cardiomyopathy; a milder childhood form with later onset, characterized by hypoketotic hypoglycemia, low mortality and rare cardiomyopathy; an adult form, with isolated skeletal muscle involvement, rhabdomyolysis and myoglobinuria, usually triggered by exercise or fasting.

ABCG5 and ABCG8 form an obligate heterodimer that mediates Mg(2+)- and ATP-dependent sterol transport across the cell membrane. Plays an essential role in the selective transport of the dietary cholesterol in and out of the enterocytes and in the selective sterol excretion by the liver into bile (PubMed:11099417, PubMed:11452359, PubMed:15054092, PubMed:27144356). Required for normal sterol homeostasis (PubMed:11099417, PubMed:11452359, PubMed:15054092). The heterodimer with ABCG5 has ATPase act

Cell membraneApical cell membrane

Gallbladder disease 4

One of the major digestive diseases. Gallstones composed of cholesterol (cholelithiasis) are the common manifestations in western countries. Most people with gallstones, however, remain asymptomatic through their lifetimes.

Could play a role in cell proliferation during neuronal differentiation and in protection against cell death

Endoplasmic reticulum membraneEndoplasmic reticulum-Golgi intermediate compartment membraneEndoplasmic reticulum

Ceroid lipofuscinosis, neuronal, 8

A form of neuronal ceroid lipofuscinosis with onset in childhood. Neuronal ceroid lipofuscinoses are progressive neurodegenerative, lysosomal storage diseases characterized by intracellular accumulation of autofluorescent liposomal material, and clinically by seizures, dementia, visual loss, and/or cerebral atrophy. The lipopigment patterns observed most often in neuronal ceroid lipofuscinosis type 8 comprise mixed combinations of granular, curvilinear, and fingerprint profiles.

Catalyzes the oxidation of medium and long chain aliphatic aldehydes to fatty acids. Active on a variety of saturated and unsaturated aliphatic aldehydes between 6 and 24 carbons in length (PubMed:18035827, PubMed:18182499, PubMed:22633490, PubMed:25047030, PubMed:9133646, PubMed:9662422). Responsible for conversion of the sphingosine 1-phosphate (S1P) degradation product hexadecenal to hexadecenoic acid (PubMed:22633490)

Microsome membraneEndoplasmic reticulum membrane

Sjoegren-Larsson syndrome

An autosomal recessive neurocutaneous disorder characterized by a combination of severe intellectual disability, spastic di- or tetraplegia and congenital ichthyosis. Ichthyosis is usually evident at birth with varying degrees of erythema and scaling, neurologic symptoms appear in the first or second year of life. Most patients have an IQ of less than 60. Additional clinical features include glistening white spots on the retina, seizures, short stature and speech defects.

A cytochrome P450 monooxygenase that plays a major role in adrenal steroidogenesis. Catalyzes the hydroxylation at C-21 of progesterone and 17alpha-hydroxyprogesterone to respectively form 11-deoxycorticosterone and 11-deoxycortisol, intermediate metabolites in the biosynthetic pathway of mineralocorticoids and glucocorticoids (PubMed:10602386, PubMed:16984992, PubMed:22014889, PubMed:25855791, PubMed:27721825). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, a

Endoplasmic reticulum membraneMicrosome membrane

Adrenal hyperplasia 3

A form of congenital adrenal hyperplasia, a common recessive disease due to defective synthesis of cortisol. Congenital adrenal hyperplasia is characterized by androgen excess leading to ambiguous genitalia in affected females, rapid somatic growth during childhood in both sexes with premature closure of the epiphyses and short adult stature. Four clinical types: 'salt wasting' (SW, the most severe type), 'simple virilizing' (SV, less severely affected patients), with normal aldosterone biosynthesis, 'non-classic form' or late-onset (NC or LOAH) and 'cryptic' (asymptomatic).

ABCG5 and ABCG8 form an obligate heterodimer that mediates Mg(2+)- and ATP-dependent sterol transport across the cell membrane (PubMed:27144356). Plays an essential role in the selective transport of dietary plant sterols and cholesterol in and out of the enterocytes and in the selective sterol excretion by the liver into bile (PubMed:11099417, PubMed:11138003, PubMed:15054092, PubMed:27144356). Required for normal sterol homeostasis (PubMed:11099417, PubMed:11138003, PubMed:15054092). The heter

Cell membraneApical cell membrane

Sitosterolemia 2

A form of sitosterolemia, an autosomal recessive metabolic disorder characterized by unregulated intestinal absorption of cholesterol, phytosterols and shellfish sterols, and decreased biliary excretion of dietary sterols into bile. Patients have hypercholesterolemia, very high levels of plant sterols in the plasma, and frequently develop tendon and tuberous xanthomas, accelerated atherosclerosis and premature coronary artery disease.

Component of chylomicrons, very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL) in plasma. Plays an important role in lipoprotein metabolism as an activator of lipoprotein lipase. Both proapolipoprotein C-II and apolipoprotein C-II can activate lipoprotein lipase. In normolipidemic individuals, it is mainly distributed in the HDL, whereas in hypertriglyceridemic individuals, predominantly found in the VLDL and LDL

Secreted

Hyperlipoproteinemia 1B

Autosomal recessive trait characterized by hypertriglyceridemia, xanthomas, and increased risk of pancreatitis and early atherosclerosis.

ATPase required for the post-translational delivery of tail-anchored (TA) proteins to the endoplasmic reticulum (PubMed:17382883). Recognizes and selectively binds the transmembrane domain of TA proteins in the cytosol. This complex then targets to the endoplasmic reticulum by membrane-bound receptors GET1/WRB and CAMLG/GET2, where the tail-anchored protein is released for insertion. This process is regulated by ATP binding and hydrolysis. ATP binding drives the homodimer towards the closed dime

CytoplasmEndoplasmic reticulumNucleus, nucleolus

Cardiomyopathy, dilated, 2H

A form of dilated cardiomyopathy, a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death. CMD2H is an autosomal recessive form characterized by rapid progression and death in early infancy.