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.

Catalyzes the hydroxylation of free fatty acids at the C-2 position to produce 2-hydroxy fatty acids, which are building blocks of sphingolipids and glycosphingolipids common in neural tissue and epidermis (PubMed:15337768, PubMed:15863841, PubMed:17355976, PubMed:22517924). FA2H is stereospecific for the production of (R)-2-hydroxy fatty acids (PubMed:22517924). Plays an essential role in the synthesis of galactosphingolipids of the myelin sheath (By similarity). Responsible for the synthesis o

Endoplasmic reticulum membraneMicrosome membrane

Spastic paraplegia 35, autosomal recessive, with or without neurodegeneration

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. SPG35 is a complicated form characterized by childhood onset of gait difficulties. It has a rapid progression and many patients become wheelchair-bound as young adults. Patients manifest cognitive decline associated with leukodystrophy. Other variable neurologic features, such as dystonia, optic atrophy, and seizures may also occur.

Ethanolaminephosphotransferase that catalyzes the transfer of phosphoethanolamine (PE) from CDP-ethanolamine to lipid acceptors, the final step in the synthesis of PE via the 'Kennedy' pathway (PubMed:17132865, PubMed:28052917, PubMed:29500230). PE is the second most abundant phospholipid of membranes in mammals and is involved in various membrane-related cellular processes (PubMed:17132865). The enzyme is critical for the synthesis of several PE species and also catalyzes the synthesis of plasm

Endoplasmic reticulum membrane

Spastic paraplegia 81, 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. SPG81 is a complicated form characterized by white matter abnormalities, hypomyelination with progressive white matter loss, delayed motor development, progressive spasticity, and impaired intellectual development and speech delay. Additional features may include bifid uvula, microcephaly, seizures, and variable ocular anomalies.

Catalyzes both the phosphorylation of dihydroxyacetone and of glyceraldehyde, and the splitting of ribonucleoside diphosphate-X compounds among which FAD is the best substrate. Represses IFIH1-mediated cellular antiviral response (PubMed:17600090)

Triokinase and FMN cyclase deficiency syndrome

An autosomal recessive disease characterized by cataracts and developmental delay that may be associated with cerebellar hypoplasia. Additional features may include liver dysfunction, microcytic anemia, and fatal cardiomyopathy with lactic acidosis following a febrile illness.

ADP:ATP antiporter that mediates import of ADP into the mitochondrial matrix for ATP synthesis, and export of ATP out to fuel the cell (PubMed:21586654, PubMed:27693233, PubMed:23173940, PubMed:30046662). Cycles between the cytoplasmic-open state (c-state) and the matrix-open state (m-state): operates by the alternating access mechanism with a single substrate-binding site intermittently exposed to either the cytosolic (c-state) or matrix (m-state) side of the inner mitochondrial membrane (By si

Mitochondrion inner membraneMembrane

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 2

A disorder characterized by progressive weakness of ocular muscles and levator muscle of the upper eyelid. In a minority of cases, it is associated with skeletal myopathy, which predominantly involves axial or proximal muscles and which causes abnormal fatigability and even permanent muscle weakness. Ragged-red fibers and atrophy are found on muscle biopsy. A large proportion of chronic ophthalmoplegias are associated with other symptoms, leading to a multisystemic pattern of this disease. Additional symptoms are variable, and may include cataracts, hearing loss, sensory axonal neuropathy, ataxia, depression, hypogonadism, and parkinsonism.

Catalyzes the first and rate-limiting reaction of the four reactions that constitute the long-chain fatty acids elongation cycle. This endoplasmic reticulum-bound enzymatic process allows the addition of 2 carbons to the chain of long- and very long-chain fatty acids (VLCFAs) per cycle. Condensing enzyme that acts specifically toward polyunsaturated acyl-CoA with the higher activity toward C18:3(n-6) acyl-CoA. May participate in the production of monounsaturated and of polyunsaturated VLCFAs of

Endoplasmic reticulum membraneCell projection, dendrite

Spinocerebellar ataxia 38

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA38 is an autosomal dominant form characterized by adult-onset of slowly progressive gait ataxia accompanied by nystagmus. Brain MRI shows cerebellar atrophy.

Lipid kinase that can phosphorylate both monoacylglycerol and diacylglycerol to form lysophosphatidic acid (LPA) and phosphatidic acid (PA), respectively (PubMed:15939762). Does not phosphorylate sphingosine (PubMed:15939762). Phosphorylates ceramide (By similarity). Phosphorylates 1,2-dioleoylglycerol more rapidly than 2,3-dioleoylglycerol (By similarity). Independently of its lipid kinase activity, acts as a component of the TIM22 complex (PubMed:28712724, PubMed:28712726). The TIM22 complex m

Mitochondrion inner membraneMitochondrion intermembrane space

Mitochondrial DNA depletion syndrome 10

An autosomal recessive mitochondrial disorder characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis. Mental development is normal, but affected individuals may die early from cardiomyopathy.

Catalyzes the initial step in triglyceride hydrolysis in adipocyte and non-adipocyte lipid droplets (PubMed:15364929, PubMed:15550674, PubMed:16150821, PubMed:16239926, PubMed:17603008, PubMed:34903883). Exhibits a strong preference for the hydrolysis of long-chain fatty acid esters at the sn-2 position of the glycerol backbone and acts coordinately with LIPE/HLS and DGAT2 within the lipolytic cascade (By similarity). Also possesses acylglycerol transacylase and phospholipase A2 activities (PubM

Lipid dropletCell membraneCytoplasm

DNA methyltransferase that methylates CpG residues (PubMed:17200670, PubMed:18754681, PubMed:21745816, PubMed:26070743). Preferentially methylates hemimethylated DNA (PubMed:21745816, PubMed:26070743). Associates with DNA replication sites in S phase maintaining the methylation pattern in the newly synthesized strand, that is essential for epigenetic inheritance (PubMed:17200670, PubMed:21745816). Associates with chromatin during G2 and M phases to maintain DNA methylation independently of repli

NucleusChromosome

Neuropathy, hereditary sensory, 1E

A neurodegenerative disorder characterized by adult onset of progressive peripheral sensory loss associated with progressive hearing impairment and early-onset dementia.

Atlastin-1 (ATL1) is a membrane-anchored GTPase that mediates the GTP-dependent fusion of endoplasmic reticulum (ER) membranes, maintaining the continuous ER network. It facilitates the formation of three-way junctions where ER tubules intersect (PubMed:14506257, PubMed:18270207, PubMed:19665976, PubMed:27619977, PubMed:34817557, PubMed:38509071). Two atlastin-1 on neighboring ER tubules bind GTP and form loose homodimers through the GB1/RHD3-type G domains and 3HB regions. Upon GTP hydrolysis,

Endoplasmic reticulum membraneGolgi apparatus membraneCell projection, axon

Spastic paraplegia 3, autosomal dominant

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.

Catalyzes the first and rate-limiting reaction of the four reactions that constitute the long-chain fatty acids elongation cycle. This endoplasmic reticulum-bound enzymatic process allows the addition of 2 carbons to the chain of long- and very long-chain fatty acids (VLCFAs) per cycle. Condensing enzyme that catalyzes the synthesis of very long chain saturated (VLC-SFA) and polyunsaturated (PUFA) fatty acids that are involved in multiple biological processes as precursors of membrane lipids and

Endoplasmic reticulum membrane

Stargardt disease 3

A form of Stargardt disease, a common hereditary macular degeneration characterized by decreased central vision, atrophy of the macula and underlying retinal pigment epithelium, and frequent presence of prominent flecks in the posterior pole of the retina. STGD3 is an autosomal dominant form with onset most commonly in the second decade of life.

Facilitates the transport of serine from the cytosol to the mitochondria by interacting with and stabilizing Sideroflexin-1 (SFXN1), a mitochondrial serine transporter, playing a fundamental role in the one-carbon cycle responsible for the synthesis of nucleotides needed for mitochondrial DNA replication (PubMed:35235340). Plays an important role in the phosphatidylglycerol (PG) remodeling that is essential for both mitochondrial function and intracellular cholesterol trafficking (PubMed:2268371

Mitochondrion membraneEndoplasmic reticulumMitochondrion

3-methylglutaconic aciduria with deafness, encephalopathy, and Leigh-like syndrome

An autosomal recessive disorder characterized by childhood onset of delayed psychomotor development or psychomotor regression, sensorineural deafness, spasticity or dystonia, and increased excretion of 3-methylglutaconic acid. Brain imaging shows cerebral and cerebellar atrophy as well as lesions in the basal ganglia reminiscent of Leigh syndrome. Laboratory studies show increased serum lactate and alanine, mitochondrial oxidative phosphorylation defects, abnormal mitochondria, abnormal phosphatidylglycerol and cardiolipin profiles in fibroblasts, and abnormal accumulation of unesterified cholesterol within cells.

Acyltransferase required to remodel newly synthesized phospholipid cardiolipin (1',3'-bis-[1,2-diacyl-sn-glycero-3-phospho]-glycerol or CL), a key component of the mitochondrial inner membrane, with tissue specific acyl chains necessary for adequate mitochondrial function (PubMed:12930833, PubMed:19164547, PubMed:19700766, PubMed:26908608, PubMed:33096711). Its role in cellular physiology is to improve mitochondrial performance (PubMed:32234310). CL is critical for the coassembly of lipids and p

Mitochondrion outer membraneMitochondrion inner membraneMitochondrion membraneCytoplasm

Barth syndrome

An X-linked disease characterized by dilated cardiomyopathy with endocardial fibroelastosis, a predominantly proximal skeletal myopathy, growth retardation, neutropenia, and organic aciduria, particularly excess of 3-methylglutaconic acid. Additional features include hypertrophic cardiomyopathy, isolated left ventricular non-compaction, ventricular arrhythmia, motor delay, poor appetite, fatigue and exercise intolerance, hypoglycemia, lactic acidosis, hyperammonemia, and dramatic late catch-up growth after growth delay throughout childhood.

Coenzyme A-dependent lysophosphatidic acid acyltransferase that catalyzes the transfer of an acyl group on a lysophosphatidic acid (PubMed:18606822). Functions preferentially with 1-oleoyl-lysophosphatidic acid followed by 1-palmitoyl-lysophosphatidic acid, 1-stearoyl-lysophosphatidic acid and 1-arachidonoyl-lysophosphatidic acid as lipid acceptor. Functions preferentially with arachidonoyl-CoA followed by oleoyl-CoA as acyl group donors (By similarity). Functions in phosphatidic acid biosynthes

CytoplasmLipid dropletCytoplasm, cytosol

Chanarin-Dorfman syndrome

An autosomal recessive inborn error of lipid metabolism with multisystemic accumulation of triglycerides although plasma concentrations are normal. Clinical characteristics are congenital generalized ichthyosis, vacuolated leukocytes, hepatomegaly, myopathy, cataracts, neurosensory hearing loss and developmental delay. The disorder presents at birth with generalized, fine, white scaling of the skin and a variable degree of erythema resembling non-bullous congenital ichthyosiform erythroderma.

Ceramide synthase that catalyzes the transfer of the acyl chain from acyl-CoA to a sphingoid base, with high selectivity toward stearoyl-CoA (octadecanoyl-CoA; C18:0-CoA) (PubMed:17977534, PubMed:23530041, PubMed:26887952, PubMed:31916624). N-acylates sphinganine and sphingosine bases to form dihydroceramides and ceramides in de novo synthesis and salvage pathways, respectively (PubMed:17977534, PubMed:23530041, PubMed:24782409, PubMed:26887952, PubMed:31916624). Plays a predominant role in skel

Endoplasmic reticulum membrane

Epilepsy, progressive myoclonic 8

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. EPM8 is an autosomal recessive form characterized by myoclonus, generalized tonic-clonic seizures and moderate to severe cognitive impairment.

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.

Transfers the sialyl group (N-acetyl-alpha-neuraminyl or NeuAc) from CMP-NeuAc to the non-reducing terminal galactose (Gal) of glycosphingolipids forming gangliosides (important molecules involved in the regulation of multiple cellular processes, including cell proliferation and differentiation, apoptosis, embryogenesis, development, and oncogenesis) (PubMed:16934889, PubMed:9822625). Mainly involved in the biosynthesis of ganglioside GM3 but can also use different glycolipids as substrate accep

Golgi apparatus membrane

Salt and pepper developmental regression syndrome

A rare autosomal recessive disorder characterized by infantile onset of severe, recurrent and refractory seizures, failure to thrive, psychomotor delay, developmental stagnation, and cortical blindness. Deafness is observed in some patients. Affected individuals have patches of skin hypo- or hyperpigmentation on the trunk, face, and extremities.

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. The SPT complex is also composed of SPTLC2 or SPTLC3 and SPTSSA or SPTSSB. Within this complex, the heterodimer with SPTLC2 or SPTLC3 forms the catalytic core (PubMed:19416851, PubMed:33558762, PubMed:36170811). The composition of the serine palmit

Endoplasmic reticulum membrane

Amyotrophic lateral sclerosis 27, juvenile

A form of amyotrophic lateral sclerosis, a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. Sensory abnormalities are absent. The pathologic hallmarks of the disease include pallor of the corticospinal tract due to loss of motor neurons, presence of ubiquitin-positive inclusions within surviving motor neurons, and deposition of pathologic aggregates. The etiology of amyotrophic lateral sclerosis is likely to be multifactorial, involving both genetic and environmental factors. The disease is inherited in 5-10% of the cases. ALS27 is an autosomal dominant form manifesting as toe walking and gait abnormalities in early childhood.

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.

Cleaves phosphorylated sphingoid bases (PSBs), such as sphingosine-1-phosphate, into fatty aldehydes and phosphoethanolamine. Elevates stress-induced ceramide production and apoptosis (PubMed:11018465, PubMed:14570870, PubMed:24809814, PubMed:28165339). Required for global lipid homeostasis in liver and cholesterol homeostasis in fibroblasts. Involved in the regulation of pro-inflammatory response and neutrophil trafficking. Modulates neuronal autophagy via phosphoethanolamine production which r

Endoplasmic reticulum membrane

RENI syndrome

An autosomal recessive, steroid-resistant nephrotic syndrome that manifests in infancy or early childhood, and progresses to end-stage renal failure within a few years. Additional clinical features include ichthyosis, adrenal insufficiency, immunodeficiency, and neurological defects. In rare cases, patients present with isolated primary adrenal insufficiency. Some patients present in utero with fetal hydrops and fetal demise.

Lysophosphatidylserine (LPS) lipase that mediates the hydrolysis of lysophosphatidylserine, a class of signaling lipids that regulates immunological and neurological processes (PubMed:25290914, PubMed:30237167, PubMed:30420694, PubMed:30643283, PubMed:30720278). Represents a major lysophosphatidylserine lipase in the brain, thereby playing a key role in the central nervous system (By similarity). Also able to hydrolyze oxidized phosphatidylserine; oxidized phosphatidylserine is produced in respo

Endoplasmic reticulum membrane

Polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataract

A slowly progressive neurologic disorder with a variable phenotype resembling Refsum disease. Clinical features include sensorineural hearing loss, visual problems related to cataracts, retinitis pigmentosa, pes cavus, ataxic and/or spastic gait disturbances with a progressive sensorimotor peripheral neuropathy. Other features include hyporeflexia, hyperreflexia, extensor plantar responses.

Atlastin-3 (ATL3) is a membrane-anchored GTPase that mediates the GTP-dependent fusion of endoplasmic reticulum (ER) membranes, maintaining the continuous ER network. It facilitates the formation of three-way junctions where ER tubules intersect (PubMed:18270207, PubMed:19665976, PubMed:24459106, PubMed:27619977, PubMed:37102997). Two atlastin-3 on neighboring ER tubules bind GTP and form loose homodimers through the GB1/RHD3-type G domains and 3HB regions. Upon GTP hydrolysis, the 3HB regions t

Endoplasmic reticulum membrane

Neuropathy, hereditary sensory, 1F

An autosomal dominant sensory neuropathy affecting the lower limbs. Distal sensory impairment becomes apparent during the second or third decade of life, resulting in painless ulceration of the feet with poor healing, which can progress to osteomyelitis, bone destruction, and amputation. There is no autonomic involvement, spasticity, or cognitive impairment.

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.

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.

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.