Effect of glycosylation on iron-mediated free radical reactions of haemoglobin

HbA(1c), the major glycosylated haemoglobin increases proportionately with blood glucose level in diabetes mellitus. Here we demonstrate that H2O2-ind uced iron release is more from HbA(1c) than that from nonglycosylated haemo globin (HbA(0)). In the presence of H2O2, HbA(1c) degrades arachidonic acid and deoxyribose more efficiently than HbA(0), which suggests that iron rel ease is more with HbA(1c) compared to HbA(0) Increased rate of oxidation of HbA(1c) in the presence of nitrobluetetrazolium is indicated by an increas e in methaemoglobin formation. HbA(1c) exhibits less peroxidase activity th an HbA(0). These findings on glycosylation-induced functional properties of haemoglobin suggest a mechanism of increased formation of free radicals an d oxidative stress in diabetes mellitus.