Catalase is an important enzyme of biological defense against oxygen toxicity. It has been detected in a wide range of aerobe. The decomposition of hydrogen peroxide catalyzed by catalase is a bi- substrate enzyme-catalyzed reaction. As Chance proposed, it is an overall first-order reaction. The decomposition of hydrogen peroxide (H2O2) catalyzed by catalase is incomplete under high substrate concentration. It is because that there exists irreversible substrate inhibition of catalase. We proposed a possible irreversible substrate-inhibitory mechanism. Using this mechanism, we studied the kinetics of catalse while the reaction was incomplete. The result is satisfactory. At 310.15K and pH=7.0, k0 and k1/k2 are calculated and to be 9.6×10^5L·mol^-1·s^-1 and 2.9×10^6, respectively.

Key words: CATALASE, THERMODYNAMICS, CALORIMETRY