title: Catabolism of glycoprotein glycans. Characterization of a lysosomal endo-N-acetyl-beta-D-glucosaminidase specific for glycans with a terminal chitobiose residue.
abstract: An endo-N-acetyl-beta-D-glucosaminidase active towards oligosaccharides with a reducing terminal [bis(N-acetylglucosamine)]residue has been characterized in rat liver. The primary structure of its reaction products was determined using high-resolution 1H-NMR spectroscopy. The enzyme is predominantly located in the lysosomal fraction, presents a maximum of activity at pH 3.5 and is completely inactive towards conjugated glycans, i.e. glycoproteins and glycopeptides as well as on glycoasparagines. These results support the existence of a new pathway for the degradation of glycoprotein glycans inside the lysosome. In particular, this enzymic activity may be the origin of oligosaccharides bearing a single terminal reducing N-acetylglucosamine residue which are excreted in the urine of patients with various exoglycosidase deficiencies.
mesh_terms: D000118:Acetylglucosaminidase / Q000032:analysis*; D000818:Animals; D004187:Disaccharides; D005260:Female; D005936:Glucans / Q000032:analysis*; D006596:Hexosaminidases / Q000032:analysis*; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D011134:Polysaccharides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004187:Disaccharides; D005936:Glucans; D011134:Polysaccharides; C032438:chitobiose; D006596:Hexosaminidases; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase