ELECTRON-SPIN RESONANCE STUDIES OF FREE-RADICAL INTERMEDIATES IN OXIDATION-REDUCTION ENZYME SYSTEMS

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Abstract
Detailed study of lactic oxidative decarboxylase shows that enzyme activity is invariably associated with a free radical, probably due to the FMN prosthetic group. When the rate of enzyme activity is varied by regulating the substrate and enzyme concentrations, the steady-state concentration of free radical varies proportionally. This behavior is to be expected of an oxidation-reduction intermediate. The effects of inhibitors on the free-radical level are equally characteristic of such an intermediate. A survey of a series of oxidation-reduction enzymes shows that in all cases free radicals occur during the course of activity. The enzymes studied are of sufficient variety and occur so widely among living cells that this evidence gives substantial support to the proposal that all biological transport is mediated by free-radical intermediates.