Monosaccharides Bound to Hemoglobins in Normal and Diabetic Individuals. Evidence for Glucose, Mannose ansd Galactose as Sugars Released by Methanolysis of the Different Hemoglobin Components

Direct evidence is given for the presence of glucose, mannose and galactose as the products of hydrolysis of hemoglobins A1a1, A1a2, A1b, A1c and A0. The presence of galactose cannot be explained by the earlier hypothesis of Amadori rearrangement and suggests the existence of further complex rearrangements. Monosaccharide content of the different hemoglobin components varies from 0.2-2.0 mol/mol of alpha beta dimer with an increase of 1.5-2.0-times in diabetic components. This increase is not accompanied by net charge differences, suggesting that additionally bound sugars are not responsible for the pI modification of these hemoglobins. The pattern of glucose, mannose and galactose ratio in normal individuals divides these hemoglobins into two classes, hemoglobins A1b, A1c and A0 (ratio 0.60:0.25:0.15) on one hand and hemoglobins A1a1 and A1a2 (ratio 0.40:0.40: 0.20) on the other. These findings suggest that diverse mechanisms for sugar binding might exist between these two classes of glycosylated hemoglobins. This difference disappears in diabetic components suggesting that the non-NH2-terminal sites are glycosylated in all components by a common mechanism. Increase in glucose at the expense of mannose and galactose, as observed in diabetics, could be an indicator of recent glycosylation.