N-acetylglucosamine-1-phosphotransferase subunit gamma (GNPTG) is a non-catalytic component of the N-acetylglucosamine-1-phosphotransferase complex. The complex is lysoosomal and a heterohexamer consisting of two alpha, two beta and two gamma subunits, and is required for the first step in the synthesis of the mannose 6-phosphate recognition marker on lysosomal acid hydrolases. The gamma subunit facilitates the addition of a second GlcNAc-P to the high mannose oligosaccharides of the substrates []. Mutations in the gene for the gamma subunit are associated with mucolipidosis type III complementation group C (MLIIIC), an autosomal recessive disease of lysosomal hydrolase trafficking [].
