N-acetylglucosamine-1-phosphate transferase, alpha/beta and gamma subunits; N-acetylglucosamine-1- (GNPTAB, GNPTG)

GlcNAc-1-phosphotransferase catalyzes the transfer of a GlcNAc-1-phosphate residue from UDP-GlcNAc to C6 positions of selected mannoses in highmannose- type oligosaccharides of the hydrolases (Goldberg and Kornfeld 1981; Natowicz et al. 1982; Varki and Kornfeld 1983). At a biological level this reaction is followed by the removal of the terminal GlcNAc by an N-acetylglucosamine-1-phosphodiester α-N-acetyl-glucosaminidase, usually referred to as “uncovering enzyme” (UCE; see Chap. 78; Article ID: 332135). Sequential action of these two enzymes results in the formation of the mannose-6-phosphate (Man-6-P) marker, a specific tag acquired by lysosomal hydrolases that ensures recognition by M6P receptors and delivery to the endosomal/lysosomal system (Braulke and Bonifacino 2009)