Glycation-induced inactivation and loss of antigenicity of catalase and superoxide dismutase

Oxidative mechanisms are thought to have a major role in several biological phenomena, including cataract formation and diabetic complications. Here we investigate the inactivation of catalase and superoxide dismutase, both powerful antioxidant enzymes, by sugars of different glycating abilities, and the loss of antigenicity that was monitored by the loss of activity after immunoprecipitation with monospecific antibodies. The anti genicity of non-glycated or glycated enzymes separated by affinity chromatography were determined by dot-blotting. Incubation with sugars resulted in a time-dependent inactivation of the enzymes. Ribose and fructose inactivated them more rapidly than glucose and glucose 6-phosphate. Glycation induced losses of antigenicity and inactivation simultaneously. The glycated enzymes had entirely lost their antigenicity compared with non-glycated enzyme. These results further support the idea that inactivation of enzyme and loss of antigenicity are simultaneous. This might occur in the pathogenesis of diabetic complications and aging.