It is made up of two alpha (α), two betas (β), and two gammas (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 cell, helps break down large molecules into smaller ones that can be reused. GlcNAc-1-phosphotransferase phosphorylates carbon 6 of one or more mannosyl residues of
N-linked glycoproteins being processed in the
Golgi apparatus. UDP-GLcNAc provides the phosphate in a reaction catalysed by this enzyme. M6P acts as an indicator of whether a hydrolase should be transported to the lysosome or not. Once a hydrolase indicates an M6P, it can be transported to a lysosome. Surprisingly some lysosomal enzymes are only tagged at a rate of 5% or lower. ==Clinical significance==