GNPTG

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.

N-acetylglucosamine-1-phosphotransferase, gamma subunit

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.

Carbohydrate phosphorylation Source: UniProtKB

Golgi apparatus; Secreted

Mucolipidosis type III complementation group C (MLIIIC):
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.
Defects in GNPTG have been suggested to play a role in susceptibility to persistent stuttering. Stuttering is a common speech disorder characterized by repetitions, prolongations, and interruptions in the flow of speech.

Cys-245 mediates the formation of the interchain disulfide bond for formation of the homodimer. Cys-142, Cys-157 and Cys-169 are involved in intramolecular disulfide bonds formation (By similarity).