COMPARATIVE KINETIC CHARACTERIZATION OF CATALASES FROM CANDIDA-BOIDINII YEAST AND BOVINE LIVER

Catalase with molecular weight 230+/-2 kD was isolated and purified fr om methylotrophic yeasts Candida boidinii by ion-exchange chromatograp hy. The kinetic characteristics of yeast and bovine liver catalases we re compared in the reaction of H2O2 decomposition using a wide range o f H2O2 concentrations (up to 0.12 M) and pH (2-10). First order rate c onstants (k, sec(-1)) were determined for both enzymes from semi-logar ithmic anamorphoses of kinetic curves of H2O2 utilization. Anamorphose s of complete kinetic curves as a function of 1/ln([H2O2](0)/[H2O2]) v ersus l/t were used for calculation of the effective rate constants of catalase inactivation during the reaction (k(in), sec(-1)) and the ra te constants of interaction of catalase complex I with the second mole cule of H2O2 (k(2), M-1.sec(-1)). The effects of initial catalase conc entrations, H2O2, and pH on k, k(2), and k(in) were similar for both e nzymes. Catalytic constant, k(2), and the efficacy expressed as a rati o k(cat)/K-m were 1.87-, 1.45-, and 1.3-fold, respectively, higher for bovine catalase than that of yeast catalase. Operational stability of yeast catalase is 3.5-fold higher than the stability of bovine catala se and much higher during cyclic decomposition of 50 mM H2O2. Enhanced operational stability and inexpensive source of its preparation open prospects for practical applications of yeast catalase for co-immobili zation with superoxide dismutase on non-toxic carriers.