Catalase in vitro.

Publisher Summary Catalase exerts a dual function: (1) decomposition of H 2 O 2 to give H 2 O and O 2 (catalytic activity) and (2) oxidation of H donors, for example, methanol, ethanol, formic acid, phenols, with the consumption of 1 mol of peroxide (peroxide activity). The kinetics of catalase does not obey the normal pattern. Measurements of enzyme activity at substrate saturation or determination of the K s is therefore impossible. In contrast to reactions proceeding at substrate saturation, the enzymic decomposition of H 2 O 2 is a first-order reaction, the rate of which is always proportional to the peroxide concentration present. Consequently, to avoid a rapid decrease in the initial rate of the reaction, the assay must be carried out with relatively low concentrations of H 2 O 2 (about 0.01 M). This chapter discusses the catalytic activity of catalase. The method of choice for biological material, however, is ultraviolet (UV) spectrophotometry. Titrimetric methods are suitable for comparative studies. For large series of measurements, there are either simple screening tests, which give a quick indication of the approximative catalase activity, or automated methods.