Characterization of hydrogenase activities associated with the molybdenum CO dehydrogenase fromOligotropha carboxidovorans

Abstract

The formation of H2 by chemolithoautrophically growing Oligotropha carboxidovorans has been identified as the result of the oxidation of CO mediated by the cytoplasmic species of the molybdenum-containing CO dehydrogenase multienzyme complex as follows: CO+H2O→CO2+H2. Purified CO dehydrogenase was shown to carry hydrogen uptake and formation activities in addition to its catabolic function which is the oxidation of CO. Among the electron donors supporting H2 formation were CO, NADH, reduced flavins and reduced viologen dyes. The reduction of protons to H2 by cytoplasmic CO dehydrogenase is interpreted as a detoxification reaction for electrons to prevent cell damage in O. carboxidovorans.