Monoamine oxidase—I: Specificity of some substrates and inhibitors

Abstract

A number of synthetic substrates and inhibitors of monoamine oxidase have been studied, using the enzyme from porcine brain. K m and V max values have been calculated for substrates using Lineweaver-Burk plots. In many cases large variations in K m and V max were observed for relatively small changes in the structure of substrates. Similar observations were made concerning K i values for some competitive inhibitors. The effects of hydrogen-ion concentration on enzyme activity are consistent with the view that unprotonated amines are the species which bind to the enzyme. This finding, together with the observation that tertiary amines can act as substrates has led to formulation of a proposed mechanism of dehydrogenation which does not depend upon intermediate formation of Schiff base from the substrate amine.