[Two forms of aldose reductase in erythrocytes from patients with insulin-dependent diabetes mellitus].

Erythrocytes of patients with insulin-dependent diabetes mellitus contained two forms of aldose reductase a and b (EC No. 1.1.1.21) (the key enzyme in the sorbitol pathway of glucose utilization) as compared with those of healthy donors in whom the form b of the enzyme was only found. The aldose reductase a exhibited a higher maximal rate (Vmax = 16.7 +/- 3.2 IU/D280) and a lower substrate affinity (Km = 6.5 = 19 mM) than the enzyme b, Vmax = 43.8 +/- 0.6 IU/D280, Km = 3.0 = 4.0 mM, respectively. More severe development of the disease was observed in the patients whose erythrocytes contained only aldose reductase a (HbA1c = 14.56 +/- 0.69%) as compared with those in whom the enzyme a and b were found (HbA1c = 11.5 +/- 0.4%). Kinetic parameters of the enzyme showed that aldose reductase a may be active in hyperglycemia of diabetes mellitus, thus contributing to intensification of the sorbitol pathway in these patients.