Spectrophotometric assay for superoxide dismutase based on the nitroblue tetrazolium reduction by glucose-glucose oxidase.

A new spectrophotometric assay of superoxide dismutase (SOD) is described. The assay is based on the SOD-mediated inhibition in the rate of nitroblue tetrazolium reduction to the blue formazan at alkaline pH. The 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 SOD. 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 commercially available reagents, rapid and easy to perform and could be used routinely for monitoring superoxide dismutase levels in purified protein fractions.