This gene encodes the gamma sunbunit of the N-acetylglucosamine-1-phosphotransferase complex. This hexameric complex, composed of alpha, beta and gamma subunits, catalyzes the first step in synthesis of a mannose 6-phosphate lysosomal recognition marker. This enzyme complex is necessary for targeting of lysosomal hydrolases to the lysosome. Mutations in the gene encoding the gamma subunit have been associated with mucolipidosis IIIC, also known as mucolipidosis III gamma.[provided by RefSeq, Feb 2010].
Function:
May recognize the substrate of GlcNAc-1-phosphotransferase but also the lysosomal proteins with mannose-6-phosphate residues.
Subunit:
Hexamer of two alpha, two beta and two gamma subunit; disulfide-linked. It is believed that the alpha and/or the beta subunit of the enzyme contain the catalytic portion and that the gamma subunit functions in recognition of the lysosomal enzymes.
Subcellular Location:
Golgi Apparatus and Secreted.
Tissue Specificity:
Widely expressed.
DISEASE:
Defects in GNPTG are the cause of mucolipidosis type III complementation group C (MLIIIC) [MIM:252605]; also known as variant pseudo-Hurler polydystrophy. MLIIIC is an 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 mental retardation. 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.
Similarity:
Contains 1 PRKCSH domain.
SWISS:
Q9UJJ9
Gene ID:
84572
Database links:
Entrez Gene: 84572 Human
Omim: 607838 Human
SwissProt: Q9UJJ9 Human
Unigene: 241575 Human
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