[Operational stability of catalase and its conjugates with aldehyde dextrans and superoxide dismutase]

Catalase, superoxide dismutase (SOD) and catalase-superoxide dismutase conjugates with aldehyde dextrans have been prepared in aqueous media and surfactant microemulsions. The catalytic activities of catalase and its conjugates were characterized by first order rate constants in successive cycles of the biocatalysts. The rate constants for catalase and its conjugates inactivation by hydrogen peroxide, kin, and the rate constants for catalase complex I interaction with H2O2, k2, were determined simultaneously from the full kinetic curves for H2O2 decomposition in 1/In[(H2O2)0/[H2O2]t)-1/t coordinates. The kin and k2 values were calculated under variable conditions of the catalase reaction and at varying concentrations of the biocatalysts and hydrogen peroxide as well as in successive cycles of the biocatalysts used for H2O2 decomposition. The utility of the kinetic parameters, kin and k2, for characterizing catalase and its conjugates inactivation and their reactivity in catalase reactions has been demonstrated. The reciprocal action of catalase and SOD on their operational stabilities in enzymatic reactions of H2O2 decomposition is discussed. Catalase conjugation to aldehyde dextrans and SOD in microemulsions enhances the stabilities of the both enzymes.