Products of digestion of tryptic M and N blood group glycopeptides with pronase

Abstract

Digestion of tryptic M and N blood group glycopeptides with pronase generated a heterogeneous mixture of smaller glycopeptides. Two NH2-terminal glycopeptides, composed of 26--28 and 18--19 amino acid residues, and three fractions containing several glycopeptides deriving from the COOH-terminal portion of tryptic glycopeptides were obtained. The characterization of pronase glycopeptides showed that most of the peptide bonds hydrolyzed by pronase were susceptible to proteolysis only in part of molecules of tryptic glycopeptides, most probably due to a microheterogeneity in their glycosylation. The similar sets of pronase glycopeptides were obtained from tryptic M and N glycopeptides, indicating that the possible heterogeneity in their glycosylation is independent of the blood group type. Only the NH2-terminal glycopeptides showed M and N blood group activity, and only the NH2-terminal glycopeptides obtained from tryptic N glycopeptide reacted with Vicia graminea anti-N lectin.