New spectrophotometric assay for assessments of catalase activity in biological samples

A novel, simple, and accurate colorimetric assay was established for assessments of catalase activity in biological fluids and tissues. H₂O₂ dissociation rates are directly proportional to catalase activity, and the principle of the present assay is based on reactions of ammonium metavanadate with H₂O₂ under acidic conditions. The resulting reduction of vanadium (V) to vanadium (III) produces a red-orange peroxovanadium complex with absorbance maxima at 452 nm. Biological samples containing catalase were incubated with 50-mM phosphate buffer solution containing 10-mM H₂O₂ as a substrate for two min. Subsequently, ammonium metavanadate in sulfuric acid was used as an indicator reagent and was added to reaction mixtures to determine remaining H₂O₂ concentrations. The precision of the present novel assay was indicated by coefficients of variation of 4.09% within runs and 2.56% between runs. Moreover, in experiments with homogenized red blood cell solutions, peroxovanate and dichromate assays of catalase activities were highly correlated (r = 0.993). In further experiments, we demonstrated application of the peroxovanadate method to assessments of catalase activity in bacterial and liver homogenates. The present method is accurate, simple, rapid, and inexpensive and can be used for routine clinical measurements and scientific investigations.