Studies on the Oligosaccharide Sequence of Ribonuclease B

Abstract

Abstract α-Mannosidase treatment of the asparaginyl oligosaccharide derivative from ribonuclease B released 5 eq of mannose and yielded a product containing asparagine, N-acetylglucosamine, and mannose in a ratio of 1:2:1. The remaining mannose residue was resistant to hydrolysis by α-mannosidase, but could be removed by a Smith degradation, a procedure which did not affect the N-acetylglucosamine residues. The resultant product chromatographed identically with 2-acetamido-4-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-N-(4-l-aspartyl)-2-deoxy-β-d-glucopyranosylamine prepared chemically by Spinola and Jeanloz (J. Biol. Chem., 245, 4158 (1970)). In addition, both synthetic and isolated compounds reacted similarly on treatment with β-N-acetylglucosaminidase and glycosyl asparaginase. Evidence is presented showing the mannose residue in the asparaginyl trisaccharide to be linked to the 3-O position of the terminal nonreducing N-acetylglucosamine and that the N-acetylglucosamines form a disaccharide identical with di-N-acetylchitobiose.