Improved assay for catalase based upon steady-state substrate concentration

Abstract

A modification of the polarographic assay for catalase is described that is based upon automatic titration of a buffered H 2O 2-catalase reaction mixture with a more concentrated H 2O 2 solution such that there is no significant change in the volume of the reaction mixture. The recorded rate of addition of the titrant required to maintain a steady-state substrate concentration yields enzyme activity measurements in terms of actual reaction rate instead of the less satisfactory rate constant for H 2O 2 decomposition, as is the case for most extant assays for catalase. An additional advantage of the new method is that the reaction can be easily carried out at considerably lower temperature and substrate concentrations than can be employed practicably in other types of assays for this enzyme. Both of these features are desirable to minimize the formation of inactive catalase-H 2O 2 complexes. The improved assay works satisfactorily for measuring catalase activity in rat tissue homogenates.