Blood Group A and H Determinants in Polyglycosyl Peptides of A1 and A2 Erythrocytes

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Abstract
Polyglycosyl peptides were isolated from delipidated erythrocyte membranes of human blood‐group A1 and A2 erythrocytes by extensive pronase digestion and gel filtration. As estimated by the amounts of N‐acetyl‐galactosamine and 2‐O‐substituted galactose residues about 85% of the possible acceptor sites (H determinants) were saturated with A determinants in A1 polyglycosyl peptides whereas only 25% of H sites were filled in A2 glycopeptides. The distribution of A and H determinants in the glycopeptides was studied by affinity chromatography with Sepharose‐bound Bandeiraea simplicifolia I‐lectin (binds blood‐group A and B determinants) and Ulex europaeus I‐lectin (binds blood‐group H determinants). About 55% of the polyglycosyl peptides contained A, H, or A and H determinants in both A1 and A2 blood subgroups. 48% of the polyglycosyl peptides of blood group A1 and 10% of A2 bound to Bs I‐lectin. 25% of the polyglycosyl peptides in A1 and 53% in A2 carried H determinants. The molecular size, monosaccharide composition and the substitution pattern of the monosaccharides in the Bs‐I‐bound polyglycosyl peptides were very similar in both A1 and A2 blood groups. The only difference was the amount of N‐acetylgalactosamine which was on the average 3.7 mol/mol in A1 and 2.5 mol/mol in A2. The active fraction was found to be heterogeneous with respect to the amount of A determinants, which varied from 1 to 6 per glycopeptide in A1 and A2 polyglycosyl peptides. The findings do not indicate a structural difference between blood‐group A1 and A2 polyglycosyl peptides and state chemically that A1 glycopeptides contain more A determinants than A2 glycopeptides.