Oxidation of NADH by vanadate plus phenylmethanesulfonyl fluoride (PMSF)

Phenylmethanesulfonyl fluoride (PMSF) enabled vanadate to catalyze the oxidation of NADH. Superoxide dismutase and manganese inhibited the oxidation, suggesting that superoxide anion played a crucial role. Since PMSF is widely used to protect enzymes from proteolytic cleavage when they are purified, attention should be paid when the toxicity of vanadate on the enzyme, whose activities are monitored by the oxidation of NADH, is evaluated or when vanadate dependent NADH oxidase is purified and assayed.