Evidence for superoxide radical production by a simple flavoprotein: glucose oxidase

Abstract

Nitroblue tetrazolium was reduced to blue formazan during the oxidation of glucose by glucose oxidase. The rate of blue color formation was dependent on the concentrations of glucose, nitroblue tetrazolium and glucose oxidase. The rate of the reaction was negligible below pH 8.4, but sharply increased with increasing pH. The reduction of nitroblue tetrazolium was inhibited by superoxide dismutase, consistent with the participation of superoxide anion radical in the reaction.