INACTIVATION OF CN,ZN-SUPEROXIDE DISMUTASE BY IN-VITRO GLYCOSYLATION AND IN ERYTHROCYTES OF DIABETIC-PATIENTS

Purified bovine Cu,Zn-superoxide dismutase was nonenzymatically glycos ylated in vitro at a rate proportional to incubation time (2 to 120 hr s) and glucose concentration (10 to 100 mM). Inverse correlation betwe en glycosylation and the enzyme activity showed that increased glycosy lation was accompanied with inactivation of the enzyme. Specific activ ities of glycosylated and non-glycosylated enzymes incubated with 100 mM glucose for 120 hrs were 1150 and 2860 units/mg protein, respective ly This indicates that nonenzymatic glycosylation declined the enzyme activity approximately to 40%. All these results were consistent with the in vivo studies that Cu,Zn-superoxide dismutase activity in erythr ocytes of non-insulin dependent diabetic patients was inversely correl ated with their plasma glucose. Inactivation of Cu,Zn-superoxide dismu tase demonstrated by both in vitro and in vivo studies may be importan t for the development of diabetic complications, because the enzyme ha s a crucial role in protecting the body against the damaging effects o f the superoxide radicals.