Inactivation of erythrocyte Cu-Zn-superoxide dismutase through nonenzymatic glycosylation.

Human erythrocyte Cu-Zn-superoxide dismutase undergoes glycation reaction in vitro and in vivo (Arai et al., 1987a; Arai et al., 1987b). In addition, an increase in the glycation of the superoxide dismutase was observed in aged erythrocytes, indicating that the glycation reaction is an age-related change under physiological conditions. In the cases of crude extracts as well as pure enzyme preparations obtained from erythrocytes of patients with Werner's syndrome, the specific activity of the glycated form expressed as units per mg Cu-Zn-superoxide dismutase protein as determined by both enzymatic assay and immunoenzymatic assay was significantly lower and the enzyme was unstable as compared to the normal form.