The function of NAGPA (N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase, Ensembl gene identifier ENSG00000103174) is as follows. Catalyzes the second step in the formation of the mannose 6- phosphate targeting signal on lysosomal enzyme oligosaccharides by removing GlcNAc residues from GlcNAc-alpha-P-mannose moieties, which are formed in the first step. Also hydrolyzes UDP-GlcNAc, a sugar donor for Golgi N-acetylglucosaminyltransferases. .