Structural Studies on Human Erythrocyte Glycoproteins

Abstract Treatment of M- or N-active sialoglycopeptides, derived from human erythrocytes, with alkaline borohydride (0.1 m NaOH-0.4 m NaBH4, room temperature, 26 hours) released 25 to 30% of the carbohydrate as low molecular weight oligosaccharides. No difference was found in the composition of oligosaccharides obtained from M- or N-active erythrocytes. The most complex oligosaccharide (Component I) was a tetrasaccharide, N-acetylneuraminyl-(2 → 3)-β-d-galactopyranosyl-(1 → 3) N-acetylneuraminyl-(2 → 6)-d-N-acetylgalactosaminitol. In addition, the following compounds were identified: N-acetylneuraminyl-(2 → 3)-β-d-galactopyranosyl-(1 → 3)-d-N-acetylgalactosaminitol (Component II); N-acetylneuraminyl-(2 → 3)-β-d-galactitol (Component III); β-d-galactopyranosyl-(1 → 3)-d-N-acetylgalactosaminitol, together with free sialic acid, galactitol, N-acetylgalactosaminitol, 3-deoxy-d-glucitol, and the reduced Kuhn chromogen. It is concluded that the major, alkali-labile oligosaccharide of sialoglycopeptides is a tetrasaccharide and that other components are degradation products thereof.