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.

As part of AP-5, a probable fifth adaptor protein complex it may be involved in endosomal transport. According to PubMed:20613862 it is a putative helicase required for efficient homologous recombination DNA double-strand break repair

CytoplasmNucleus

Spastic paraplegia 48, 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.

Thiol protease involved in osteoclastic bone resorption and may participate partially in the disorder of bone remodeling. Displays potent endoprotease activity against fibrinogen at acid pH. May play an important role in extracellular matrix degradation. Involved in the release of thyroid hormone thyroxine (T4) by limited proteolysis of TG/thyroglobulin in the thyroid follicle lumen (PubMed:11082042)

LysosomeSecretedApical cell membrane

Pycnodysostosis

A rare autosomal recessive bone disorder characterized by deformity of the skull, maxilla and phalanges, osteosclerosis, and fragility of bone.

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.

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.

May have a role in promoting tumor progression. May block the TGFB1-enhanced cell growth

SecretedLysosome

Mucopolysaccharidosis 9

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPS9 is an autosomal recessive form characterized by high hyaluronan concentration in the serum. Clinical features include periarticular soft tissue masses, mild short stature and acetabular erosions, and absence of neurological or visceral involvement.

Removes terminal alpha-N-acetylgalactosamine residues from glycolipids and glycopeptides. Required for the breakdown of glycolipids

Lysosome

Schindler disease

Form of NAGA deficiency characterized by early-onset neuroaxonal dystrophy and neurological signs (convulsion during fever, epilepsy, psychomotor retardation and hypotonia). NAGA deficiency is typically classified in three main phenotypes: NAGA deficiency type I (Schindler disease or Schindler disease type I) with severe manifestations; NAGA deficiency type II (Kanzazi disease or Schindler disease type II) which is mild; NAGA deficiency type III (Schindler disease type III) characterized by mild-to-moderate neurologic manifestations. NAGA deficiency results in the increased urinary excretion of glycopeptides and oligosaccharides containing alpha-N-acetylgalactosaminyl moieties. Inheritance is autosomal recessive.

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.

Lysosome

Mucopolysaccharidosis 4A

A form of mucopolysaccharidosis type 4, an autosomal recessive lysosomal storage disease characterized by intracellular accumulation of keratan sulfate and chondroitin-6-sulfate. Key clinical features include short stature, skeletal dysplasia, dental anomalies, and corneal clouding. Intelligence is normal and there is no direct central nervous system involvement, although the skeletal changes may result in neurologic complications. There is variable severity, but patients with the severe phenotype usually do not survive past the second or third decade of life.

Nonselective cation channel probably playing a role in the regulation of membrane trafficking events and of metal homeostasis (PubMed:11013137, PubMed:12459486, PubMed:14749347, PubMed:15336987, PubMed:18794901, PubMed:25720963, PubMed:27623384, PubMed:29019983). Acts as a Ca(2+)-permeable cation channel with inwardly rectifying activity (PubMed:25720963, PubMed:29019983). Proposed to play a major role in Ca(2+) release from late endosome and lysosome vesicles to the cytoplasm, which is importan

Late endosome membraneLysosome membraneCytoplasmic vesicle membraneCell projection, phagocytic cupCytoplasmic vesicle, phagosome membraneCell membrane

Mucolipidosis 4

An autosomal recessive lysosomal storage disorder characterized by severe psychomotor retardation and ophthalmologic abnormalities, including corneal opacity, retinal degeneration and strabismus. Storage bodies of lipids and water-soluble substances are seen by electron microscopy in almost every cell type of the patients. Most patients are unable to speak or walk independently and reach a maximal developmental level of 1-2 years. All patients have constitutive achlorhydia associated with a secondary elevation of serum gastrin levels.

Exoglycosidase that cleaves the single beta-linked mannose residue from the non-reducing end of all N-linked glycoprotein oligosaccharides

Lysosome

Mannosidosis, beta A, lysosomal

An autosomal recessive lysosomal storage disease of glycoprotein catabolism. Clinical features are heterogeneous with a wide range of symptoms and age of onset. The disease is associated with a range of neurological involvement, including various degrees of intellectual disability in most of the cases, hearing loss and speech impairment, hypotonia, epilepsy and peripheral neuropathy. Affected individuals have a profound reduction in beta A mannosidase activity in plasma, fibroblasts and leukocytes.

Endoplasmic reticulum membraneEndoplasmic reticulum

Ceroid lipofuscinosis, neuronal, 6

An autosomal recessive form of neuronal ceroid lipofuscinosis. 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 6 comprise mixed combinations of granular, curvilinear, and fingerprint profiles.

Catalyzes the hydrolysis of pseudosubstrates such as p-nitrocatechol sulfate and p-nitrophenyl sulfate (PubMed:23986440). Catalyzes the hydrolysis of the 2-sulfate groups of the 2-O-sulfo-D-glucuronate residues of chondroitin sulfate, heparin and heparitin sulfate (PubMed:28055182, PubMed:34916232). Acts selectively on 2-sulfoglucuronate and lacks activity against 2-sulfoiduronate (PubMed:28055182)

SecretedLysosome

Mucopolysaccharidosis 10

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPS10 is an autosomal recessive childhood-onset disorder. Clinical features include disproportionate short-trunk short stature and skeletal, cardiac, and ophthalmologic abnormalities.

Hydrolyzes 6-sulfate groups in N-acetyl-d-glucosaminide units of heparin sulfate and keratan sulfate

Lysosome

Mucopolysaccharidosis 3D

A form of mucopolysaccharidosis type 3, an autosomal recessive lysosomal storage disease due to impaired degradation of heparan sulfate. MPS3 is characterized by severe central nervous system degeneration, but only mild somatic disease. Onset of clinical features usually occurs between 2 and 6 years; severe neurologic degeneration occurs in most patients between 6 and 10 years of age, and death occurs typically during the second or third decade of life.

Involved in the degradation of heparan sulfate

Lysosome

Mucopolysaccharidosis 3B

A form of mucopolysaccharidosis type 3, an autosomal recessive lysosomal storage disease due to impaired degradation of heparan sulfate. MPS3 is characterized by severe central nervous system degeneration, but only mild somatic disease. Onset of clinical features usually occurs between 2 and 6 years; severe neurologic degeneration occurs in most patients between 6 and 10 years of age, and death occurs typically during the second or third decade of life.

Non-catalytic subunit of the N-acetylglucosamine-1-phosphotransferase complex, an enzyme that catalyzes the formation of mannose 6-phosphate (M6P) markers on high mannose type oligosaccharides in the Golgi apparatus. Binds and presents the high mannose glycans of the acceptor to the catalytic alpha and beta subunits (GNPTAB). Enhances the rate of N-acetylglucosamine-1-phosphate transfer to the oligosaccharides of acid hydrolase acceptors

SecretedGolgi apparatus

Mucolipidosis type III complementation group C

Autosomal recessive disease of lysosomal hydrolase trafficking. Unlike the related diseases, mucolipidosis II and IIIA, the enzyme affected in mucolipidosis IIIC (GlcNAc-phosphotransferase) retains full transferase activity on synthetic substrates but lacks activity on lysosomal hydrolases. Typical clinical findings include stiffness of the hands and shoulders, claw-hand deformity, scoliosis, short stature, coarse facies, and mild intellectual disability. Radiographically, severe dysostosis multiplex of the hip is characteristic and frequently disabling. The clinical diagnosis can be confirmed by finding elevated serum lysosomal enzyme levels and/or decreased lysosomal enzyme levels in cultured fibroblasts.

Catalyzes the formation of mannose 6-phosphate (M6P) markers on high mannose type oligosaccharides in the Golgi apparatus. M6P residues are required to bind to the M6P receptors (MPR), which mediate the vesicular transport of lysosomal enzymes to the endosomal/prelysosomal compartment

Golgi apparatus membrane

Mucolipidosis type II

Fatal, autosomal recessive, lysosomal storage disorder characterized by severe clinical and radiologic features, peculiar fibroblast inclusions, and no excessive mucopolysacchariduria. Congenital dislocation of the hip, thoracic deformities, hernia, and hyperplastic gums are evident soon after birth.

Alpha-L-fucosidase is responsible for hydrolyzing the alpha-1,6-linked fucose joined to the reducing-end N-acetylglucosamine of the carbohydrate moieties of glycoproteins

Lysosome

Fucosidosis

An autosomal recessive lysosomal storage disease characterized by accumulation of fucose-containing glycolipids and glycoproteins in various tissues. Clinical signs include facial dysmorphism, dysostosis multiplex, moderate hepatomegaly, severe intellectual deficit, deafness, and according to age, angiokeratomas.

Lysosomal membrane glycoprotein which plays an important role in lysosome biogenesis, lysosomal pH regulation and autophagy (PubMed:11082038, PubMed:18644871, PubMed:24880125, PubMed:27628032, PubMed:36586411, PubMed:37390818, PubMed:8662539). Acts as an important regulator of lysosomal lumen pH regulation by acting as a direct inhibitor of the proton channel TMEM175, facilitating lysosomal acidification for optimal hydrolase activity (PubMed:37390818). Plays an important role in chaperone-media

Lysosome membraneEndosome membraneCell membraneCytoplasmic vesicle, autophagosome membrane

Danon disease

DAND is a lysosomal glycogen storage disease characterized by the clinical triad of cardiomyopathy, vacuolar myopathy and intellectual disability. It is often associated with an accumulation of glycogen in muscle and lysosomes.

Cystine/H(+) symporter that mediates export of cystine, the oxidized dimer of cysteine, from lysosomes (PubMed:11689434, PubMed:15128704, PubMed:18337546, PubMed:22232659, PubMed:29467429, PubMed:33208952, PubMed:36113465). Plays an important role in melanin synthesis by catalyzing cystine export from melanosomes, possibly by inhibiting pheomelanin synthesis (PubMed:22649030). In addition to cystine export, also acts as a positive regulator of mTORC1 signaling in kidney proximal tubular cells, v

Lysosome membraneMelanosome membraneCell membrane

Cystinosis, nephropathic type

A form of cystinosis, a lysosomal storage disease due to defective transport of cystine across the lysosomal membrane. This results in cystine accumulation and crystallization in the cells causing widespread tissue damage. The classical nephropathic form has onset in the first year of life and is characterized by a polyuro-polydipsic syndrome, marked height-weight growth delay, generalized impaired proximal tubular reabsorptive capacity, with severe fluid-electrolyte balance alterations, renal failure, ocular symptoms and other systemic complications.

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.

Can hydrolyze a variety of glycan substrates containing terminal alpha-mannosidic linkages. Cleaves alpha 1,2-, alpha 1,3-, and alpha 1,6-linked mannose residues on oligosaccharides generated by N-glycoprotein degradation pathways

Lysosome lumenSecreted

Mannosidosis, alpha B, lysosomal

A lysosomal storage disease characterized by accumulation of unbranched oligosaccharide chains. This accumulation is expressed histologically as cytoplasmic vacuolation predominantly in the CNS and parenchymatous organs. Depending on the clinical findings at the age of onset, a severe infantile (type I) and a mild juvenile (type II) form of alpha-mannosidosis are recognized. There is considerable variation in the clinical expression with intellectual disability, recurrent infections, impaired hearing and Hurler-like skeletal changes being the most consistent abnormalities.

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.

Multifunctional anion transporter that operates via two distinct transport mechanisms, namely proton-coupled anion cotransport and membrane potential-dependent anion transport (PubMed:15510212, PubMed:21781115, PubMed:22778404, PubMed:23889254). Electroneutral proton-coupled acidic monosaccharide symporter, with a sugar to proton stoichiometry of 1:1. Exports glucuronic acid and free sialic acid derived from sialoglycoconjugate degradation out of lysosomes, driven by outwardly directed lysosomal

Basolateral cell membraneCytoplasmic vesicle, secretory vesicle, synaptic vesicle membraneLysosome membrane

Salla disease

Sialic acid storage disease (SASD). SASDs are autosomal recessive neurodegenerative disorders characterized by hypotonia, cerebellar ataxia and intellectual disability. They are caused by a defect in the metabolism of sialic acid which results in increased urinary excretion of unconjugated sialic acid, specifically N-acetylneuraminic acid. Enlarged lysosomes are seen on electron microscopic studies. Clinical symptoms of SD present usually at age less than 1 year and progression is slow.

Catalyzes a step in lysosomal heparan sulfate degradation

Lysosome

Mucopolysaccharidosis 3A

A severe form of mucopolysaccharidosis type 3, an autosomal recessive lysosomal storage disease due to impaired degradation of heparan sulfate. MPS3 is characterized by severe central nervous system degeneration, but only mild somatic disease. Onset of clinical features usually occurs between 2 and 6 years; severe neurologic degeneration occurs in most patients between 6 and 10 years of age, and death occurs typically during the second or third decade of life. MPS3A is characterized by earlier onset, rapid progression of symptoms and shorter survival.

Lysosomal enzyme involved in the degradation pathway of dermatan sulfate and heparan sulfate

Lysosome

Mucopolysaccharidosis 2

An X-linked lysosomal storage disease characterized by intracellular accumulation of heparan sulfate and dermatan sulfate and their excretion in urine. Most children with MPS2 have a severe form with early somatic abnormalities including skeletal deformities, hepatosplenomegaly, and progressive cardiopulmonary deterioration. A prominent feature is neurological damage that presents as developmental delay and hyperactivity but progresses to intellectual disability and dementia. They die before 15 years of age, usually as a result of obstructive airway disease or cardiac failure. In contrast, those with a mild form of MPS2 may survive into adulthood, with attenuated somatic complications and often without intellectual disability.

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

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.

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.

Catalyzes the removal of sialic acid (N-acetylneuraminic acid) moieties from glycoproteins and glycolipids. To be active, it is strictly dependent on its presence in the multienzyme complex. Appears to have a preference for alpha 2-3 and alpha 2-6 sialyl linkage

Lysosome membraneLysosome lumenCell membraneCytoplasmic vesicleLysosome

Sialidosis

Lysosomal storage disease occurring as two types with various manifestations. Type 1 sialidosis (cherry red spot-myoclonus syndrome or normosomatic type) is late-onset and it is characterized by the formation of cherry red macular spots in childhood, progressive debilitating myoclonus, insiduous visual loss and rarely ataxia. The diagnosis can be confirmed by the screening of the urine for sialyloligosaccharides. Type 2 sialidosis (also known as dysmorphic type) occurs as several variants of increasing severity with earlier age of onset. It is characterized by the presence of abnormal somatic features including coarse facies and dysostosis multiplex, vertebral deformities, intellectual disability, cherry-red spot/myoclonus, sialuria, cytoplasmic vacuolation of peripheral lymphocytes, bone marrow cells and conjunctival epithelial cells.

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.

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.

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

Lysosome

Mucopolysaccharidosis 1H

A severe form of mucopolysaccharidosis type 1, a rare lysosomal storage disease characterized by progressive physical deterioration with urinary excretion of dermatan sulfate and heparan sulfate. Patients with MPS1H usually present, within the first year of life, a combination of hepatosplenomegaly, skeletal deformities, corneal clouding and severe intellectual disability. Obstructive airways disease, respiratory infection and cardiac complications usually result in death before 10 years of age.

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.

Essential for the degradation of glycogen in lysosomes (PubMed:14695532, PubMed:18429042, PubMed:1856189, PubMed:7717400). Has highest activity on alpha-1,4-linked glycosidic linkages, but can also hydrolyze alpha-1,6-linked glucans (PubMed:29061980)

LysosomeLysosome membrane

Pompe disease, infantile-onset

An early-onset form of Pompe disease, an autosomal recessive lysosomal storage disease characterized by lysosomal alpha-glucosidase deficiency, a broad clinical spectrum and age at onset ranging from infancy to adulthood. The classic early-onset form of IOPD presents at birth with massive accumulation of glycogen in muscle, heart and liver. Cardiomyopathy and muscular hypotonia are the cardinal features of this form whose life expectancy is less than two years. A milder infantile form manifests as progressive muscular disorder of childhood and patients have better prognosis.

Removes sulfate groups from chondroitin-4-sulfate (C4S) and regulates its degradation (PubMed:19306108). Involved in the regulation of cell adhesion, cell migration and invasion in colonic epithelium (PubMed:19306108). In the central nervous system, is a regulator of neurite outgrowth and neuronal plasticity, acting through the control of sulfate glycosaminoglycans and neurocan levels (By similarity)

LysosomeCell surface

Mucopolysaccharidosis 6

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPS6 is an autosomal recessive form characterized by intracellular accumulation of dermatan sulfate. Clinical features can include abnormal growth, short stature, stiff joints, skeletal malformations, corneal clouding, hepatosplenomegaly, and cardiac abnormalities.

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).

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.

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.

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.

Lysosomal acetyltransferase that acetylates the non-reducing terminal alpha-glucosamine residue of intralysosomal heparin or heparan sulfate, converting it into a substrate for luminal alpha-N-acetyl glucosaminidase

Lysosome membrane

Mucopolysaccharidosis 3C

A form of mucopolysaccharidosis type 3, an autosomal recessive lysosomal storage disease due to impaired degradation of heparan sulfate. MPS3 is characterized by severe central nervous system degeneration, but only mild somatic disease. Onset of clinical features usually occurs between 2 and 6 years; severe neurologic degeneration occurs in most patients between 6 and 10 years of age, and death occurs typically during the second or third decade of life.

Plays an important role in the degradation of dermatan and keratan sulfates

Lysosome

Mucopolysaccharidosis 7

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPS7 is an autosomal recessive form with a highly variable phenotype, ranging from severe lethal hydrops fetalis to mild forms with survival into adulthood. Most patients with the intermediate phenotype show hepatomegaly, skeletal anomalies, coarse facies, and variable degrees of mental impairment.