N-Acetylglucosamine-1-Phosphate Transferase Gamma (GNPTg)

GNPTg 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. The deduced mature GNPTAG protein has 281 amino acids and a molecular mass of 31 kD. It contains 2 N-glycosylation sites. Northern blot analysis detected a single 1.3-kb transcript in all 8 tissues examined. Additional transcripts up to 7.5 kb were found in lung.