Action of trifluoromethanesulfonic acid on highly glycosylated regions of human bronchial mucins.

Highly glycosylated glycopeptides were prepared from human bronchial mucus. They were heterogeneous and contained an average of 45 residues of glycosylated hydroxyamino acid per 100 amino acid residues. The kinetics of deglycosylation of these glycopeptides by trifluoromethanesulfonic acid-anisole mixtures at 25 degrees was monitored by chemical analysis and by polyacrylamide gel electrophoresis. The peripheral sugars were almost completely cleaved in 45 min with 3:2 and 2:1 CF3SO3H-anisole. A maximum of 75% of the O-linked N-acetylgalactosamine residues were released and mixtures of glycopeptides and peptides were obtained. Increasing the reaction time caused peptide bond cleavage. Rather mild conditions (1.2:1 CF3SO3H-anisole at 25 degrees for 90 min) gave limited deglycosylation of highly glycosylated bronchial glycopeptides, allowing the uncovering of GalNAc-peptide linkages and peptide regions able to induce the formation of specific antibodies in the rabbit.