Malate Dehydrogenases of Ox Kidney

Abstract

Kinetics of malate dehydrogenases of ox kidney were studied by means of three experimental models: bisubstrate kinetics, product inhibition and use of a powerful competitive inhibitor, β‐monofluoro‐oxalacetate. Application of Dalziel's treatment of kinetic parameters and Cleland's interpretations of product inhibition as well as criteria of competitive inhibition by fluoro‐oxal‐acetate yielded results which exclude reaction mechanisms other than compulsory ordered addition. Both isozymes exhibit identical idealized kinetics, provided anomalies of the mitochondrial enzyme (due to high degree of sensitivity to ionic environment) are simplified by experimental design. Anomalies of kinetics of the mitochondrial enzyme, caused by changes in ionic environment are probably consequences of conformational alterations.