A glucose transfer from membrane glycoconjugates to haemoglobin in isolated young red blood cells: another biosynthetic way for glycosylated haemoglobins.

Human red blood cells (RBC) are separated by centrifugation into young and old ones, as demonstrated by lower enzymatic activities and lower potassium content of the older ones. The young RBC fraction represents 5% of total RBC. After incubation for 24 h in a neutral buffer, the young RBC HbA1c content increases significantly from 4.2 to 5.2% of total Hb. No increase is found in the case of old RBC. When young RBC have been extracted for 1 h by a neutral buffer prior to incubation, there is no more increase of HbA1c. The extract contains a glycoconjugate that is both soluble in neutral buffers and in chloroform. A glycolipid extractable from the young RBC membrane contributes to HbA1c formation but disappears from old RBC, in which glycosylation by free glucose occurs. These processes are stereospecific.