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.

Cleaves the GlcNAc-Asn bond which joins oligosaccharides to the peptide of asparagine-linked glycoproteins

Lysosome

Aspartylglucosaminuria

An inborn lysosomal storage disease causing excess accumulation of glycoasparagine in the body tissues and its increased excretion in urine. Clinical features include mild to severe intellectual disability manifesting from the age of two, coarse facial features and mild connective tissue abnormalities.

Protective protein appears to be essential for both the activity of beta-galactosidase and neuraminidase, it associates with these enzymes and exerts a protective function necessary for their stability and activity. This protein is also a carboxypeptidase and can deamidate tachykinins

Lysosome

Galactosialidosis

A lysosomal storage disease associated with a combined deficiency of beta-galactosidase and neuraminidase, secondary to a defect in cathepsin A. All patients have clinical manifestations typical of a lysosomal disorder, such as coarse facies, cherry red spots, vertebral changes, foam cells in the bone marrow, and vacuolated lymphocytes. Three phenotypic subtypes are recognized. The early infantile form is associated with fetal hydrops, edema, ascites, visceromegaly, skeletal dysplasia, and early death. The late infantile type is characterized by hepatosplenomegaly, growth retardation, cardiac involvement, and a normal or mildly affected mental state. The juvenile/adult form is characterized by myoclonus, ataxia, angiokeratoma, intellectual disability, neurologic deterioration, absence of visceromegaly, and long survival.

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.

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.

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.

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.