Influence of different types of effectors on the kinetic parameters of suicide inactivation of catalase by hydrogen peroxide

The effects of cyanide and azide ions (class A), sodium-n-dodecyl sulphate (SDS) and 2-mercaptoethanol (class B), 3-aminotriazole (class C) and NADPH (class D) on the initial activity (a(i)), inactivation rate constant (k(i)) and the partition ratio (I.) Of bovine liver catalase reaction with its su icide substrate, hydrogen peroxide, were studied in 50 mM sodium phosphate buffer, pH 7.0 at 27 degrees C. The above kinetic parameters were determine d by processing the progress curve data. In class A, which contains fast an d reversible inhibitors of catalase, a proportional decrease in a(i) and k( i) was observed by inhibitors, so that the r remained constant. In class B, which contains slow and irreversible inactivators, a decrease in a(i) and constancy of k(i) and r were observed when catalase was incubated in the pr esence of such inactivators for a determined time. In class C, containing e ffector which can combine with intermediate compound I, a(i) was relatively unchanged but an increase in k(i) and a decrease in r were observed. In cl ass D, containing effector which reduces compound I to ferricatalase, a(i) was not affected significantly but some decrease in k(i) was detected which was linked with an increase in r. These results demonstrate that different classes of effecters affect the determined kinetic parameters of catalase in various ways. Thus, determination of such parameters by simple kinetic e xperiments can be carried out for classification of the agents which have a n effect on the kinetics of catalase. (C) 1999 Elsevier Science B.V. All ri ghts reserved.