OPERATIONAL STABILITY OF CATALASE AND ITS CONJUGATES WITH ALDEHYDE DEXTRANS AND SUPEROXIDE-DISMUTASE

Conjugates of catalase, superoxide dismutase (SOD), and both enzymes w ith aldehyde dextrans have been synthesized in aqueous media and surfa ctant microemulsions in heptane. The catalytic activities of catalase and its conjugates are characterized by first-order rate constants of H2O2 (50 mM) consumption in successive cycles of the use of the biocat alysts. Rate constants for the inactivation of catalase and its conjug ates by hydrogen peroxide (k(in)) and rate constants for the interacti on of catalase complex I with H2O2 (k(2)) were determined simultaneous ly from full kinetic curves of H2O2 consumption in 1/ln([H2O2](0)/[H2O 2](t)) versus 1/t coordinates. Values of k(in) and k(2) were determine d for different conditions of the catalase reaction at various concent rations of the biocatalysts and hydrogen peroxide and in successive cy cles of the use of the biocatalysts for H2O2 decomposition. The utilit y of the kinetic parameters k(in) and k(2) for characterizing the inac tivation of catalase and its conjugates and their reactivity in catala se reactions is demonstrated. The mutual influence of catalase and SOD on their operational stabilities in enzymatic reactions of H2O2 decom position is discussed. The conjugation of catalase with aldehyde dextr ans and SOD in microemulsions enhances the stabilities of both enzymes .