Electron-transport system of Vibrio succinogenes: I. Enzymes and cytochromes of the electron-transport system

Abstract

Enzyme systems responsible for the oxidation of formate and H2 by fumarate and O2 have been demonstrated and partially characterized in cell-free extracts of the cytochrome containing anaerobic vibrio, Vibrio succinogenes. The formic dehydrogenase and hydrogenase are similar to those found in Escherichia coli. Oxidase and peroxidase systems involving formate and H2 were demonstrated. Pyridine nucleotides are not involved in any of these systems. During the oxidation of formate by O2, small amounts of H2O2 are formed.Cytochromes of the b and c types are shown to be present in cells grown with formate as an energy source and either fumarate or nitrate as an electron acceptor. Some of the chemical characteristics of the cytochromes were determined. The protoheme of the cytochrome of the b type was isolated and identified. The cytochrome of the c type was partially reduced by ascorbate. Both cytochromes could be reduced by H2 or formate and the cytochrome of the b type could be oxidized by fumarate suggesting a catalytic role for this cytochrome in fumarate reduction. Both cytochromes were partially reduced by succinate.