It is made up of two alpha (α), two beta (β), and two gamma (γ) subunits. GNPTAB produces the alpha and beta subunits, GNPTG produces the gamma subunit. GlcNAc-1-phosphotransferase functions to prepare newly made enzymes for lysosome transportation (lysosomal hydrolases to the lysosome). Lysosomes, a part of an animal cells, helps break down large molecules into smaller ones that can be reused. GlcNAc-1-phosphotransferase catalyzes the N-linked glycosylation of asparagine residues with a molecule called mannose-6-phosphate (M6P). M6P acts as indicator whether a hydrolase should be transported to the lysosome or not. Once a hydrolase has the indication from an M6P, it can be transported to a lysosome. Surprisingly some lyosomal enzyme are only tagged at a rate of 5% or lower.

It is associated with the following conditions:^[1][2]

• mucolipidosis II alpha/beta (I-cell disease) – GNPTAB
• mucolipidosis III alpha/beta (pseudo-Hurler polydystrophy) – GNPTAB
• mucolipidosis III gamma – GNPTG
• stuttering (Kang et al., 2010)

In melanocytic cells GNPTG gene expression may be regulated by MITF.^[3]

Kang, C., Riazuddin, S., Mundorff, J., Krasnewich, D., Friedman, P., Mullikin, J.C., and Drayna, D. (2010). Mutations in the Lysosomal Enzyme–Targeting Pathway and Persistent Stuttering. New England Journal of Medicine 362, 677-685.

• GeneReviews/NCBI/NIH/UW entry on Mucolipidosis III Alpha/Beta
• GeneReviews/NIH/NCBI/UW entry on Mucolipidosis II
• GeneReviews/NIH/NCBI/UW entry on Mucolipidosis III Gamma
• N-acetylglucosamine-1-phosphate+transferase at the US National Library of Medicine Medical Subject Headings (MeSH)
• EC 2.7.8.15