Abstract
The role of -SH group of beef liver catalase was studied, especially in respect to the kinetic constants in the reactions of the propyl hydrogen peroxide (PrOOH) complex compound I formation and decomposition. Masking of 6 -SH groups per mole, that was titrated in the native state with PCM B, by S-carbamylmethylation did not affect the initial rate of catalatic H2O2 decomposition and the rate of the compound I formation, but it reduced the reaction rates of the compound I towards electron donor (ethanol) and of spontaneous decomposition. An accelerated inactivation of the masked catalase by H2O2 is discussed in terms of the inactive compound II formation as a result of reduced reactivity of the compound I with substrate in a catalatic or peroxidatic way.
