Glycopeptides isolated from bovine submaxillary mucin

Abstract

Extensive pronase digestion of the desialized bovine submaxillary major mucin (BSM) resulted in a mixture of glycopeptides. Separation of the glycopeptides into nine fractions, fractions a to i, was achieved by linear gradient elution at constant pH (2.6) of 0.05–0.2 m pyridine-formate buffer from Dowex 50-X2 (pyridinium form). Glycopeptide b 6 was isolated from fraction b by preparative high-voltage paper electrophoresis, and glycopeptides g 5and e 7 from fractions g and e, respectively, by preparative high-voltage paper electrophoresis and preparative paper chromatography, in succession. Homogeneity of these glycopeptides was shown by high-voltage paper electrophoresis at pH 1.9, 3.7, and 6.5 and by paper chromatography. The results of the N-terminal analysis by dansylation method with or without sequential Edman degradation and the analytical data before and after a β-elimination reaction of glycopeptides b 6, g 5, and e 7 indicated the structures of these glycopeptides as follows: Glycopeptide b 6, seryl-( O-α- N-acetylgalactosaminyl-)-serine; glycopeptide g 5, glycyl-( O-α- N-acetylgalactosaminyl-)-serine; glycopeptide e 7, seryl-( O-α- N-acetylgalactosaminyl-)-threonyl-glycyl-( O-α- N-acetylgalactosaminyl-)-serine.