Demonstration of the enzymatic mechanisms of alpha-N-acetyl-D-glucosamine-1-phosphodiester N-acetylglucosaminidase (formerly called alpha-N-acetylglucosaminylphosphodiesterase) and lysosomal alpha-N-acetylglucosaminidase.
An enzyme that is capable of removing the outer N-acetylglucosamine residues from phosphodiesters present on the high-mannose-type oligosaccharides of newly synthesized lysosomal enzymes has been described. This enzyme has been called an alpha-N-acetylglucosaminylphosphodiesterase, based upon its substrate specificity and on inhibitor studies. In this study it is demonstrated by the 18O enrichment method that the enzyme cleaves the C-O bond rather than the O-P bond, and therefore acts by a glycosidase type of mechanism. In addition, the enzyme has no significant activity toward alpha-N-acetylglucosamine 1-phosphate, and therefore requires an underlying phosphodiester for activity. In accordance with the IUB recommendations for enzyme nomenclature, it is therefore suggested that the enzyme be renamed alpha-N-acetyl-D-glucosamine-1-phosphodiester N-acetylglucosaminidase (systematic name, 2-acet-amido-2-deoxy-alpha-D-glucose 1-phosphodiester acetamidodeoxyglucohydrolase). For convenience, the trivial name phosphodiester glycosidase is proposed. Lysosomal alpha-N-acetylglucosaminidase also has a glycosidase type of mechanism but it is active toward alpha-N-acetylglucosamine 1-phosphate as well as phosphodiesters with outer N-acetylglucosamine residues.
D000118:Acetylglucosaminidase / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D006596:Hexosaminidases / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology*; D010727:Phosphoric Diester Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D013552:Swine; D009626:Terminology as Topic
D010727:Phosphoric Diester Hydrolases; C026645:N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase; D006596:Hexosaminidases; D000118:Acetylglucosaminidase