The Carbohydrate Structure of a Glycopeptide Released by the Action of Plasma Kallikrein on Bovine Plasma High-Molecular-Weight Kininogen

Abstract

Fragment 1, released from bovine plasma high-molecular-weight kininogen by the action of plasma kallikrein, is a glycopeptide with approximately 3 mol of each of N-acetylgalactosamine, galactose and sialic acid in one molecule. All these sugars were in the T-1 fragment obtained by tryptic digestion of fragment 1. Sialic acid can be completely released from the T-1 fragment by sialidase digestion. When this sialic acid-free T-l fragment was incubated with purified diplococcal endo-α-N-acetylgalactosaminidase, all remaining sugars were released as a disaccharide. By Smith degradation and β-galactosidase digestion, the structure of this disaccharide was found to be Gal β1→3Ga1NAc.
Methylation analysis of the trisaccharide released from fragment T-1 by alkaline borohydride treatment indicated that all the galactose was obtained as the 2, 4, 6-tri-O-methyl derivative. Based on this evidence, the complete structure of the carbohydrate moieties of fragment 1 was proposed as Sialylα2→3Galβ1→3GalNAc. In addition, small amounts of a tetrasaccharide, Sialylα2→3Galβ1→3 (Sialylα2→6) GalNAc also occurred as a carbohydrate chain of fragment 1.