SPECTROPHOTOMETRIC ASSAY FOR SUPEROXIDE-DISMUTASE BASED ON THE NITROBLUE TETRAZOLIUM REDUCTION BY GLUCOSE-GLUCOSE OXIDASE

A new spectrophotometric assay of superoxide dismutase(SOD) is describ ed. The assay is based on the SOD-mediated inhibition in the rate of n itroblue tetrazolium reduction to the blue formazan at alkaline pH. Th e optimized assay of SOD is performed in 50 mM glycine-NaOH buffer, pH 9.5, at 25 degrees C. The SOD concentration is determined from the V/ v ratio of rates measured in the absence (V) or the presence (v) of SO D. One unit of SOD has been defined as the concentration that decrease the rate to 50% (V/v = 2). The assay is simple, sensitive, uses comme rcially available reagents, rapid and easy to perform and could be use d routinely for monitoring superoxide dismutase levels in purified pro tein fractions.