Carbon monoxide dehydrogenase from Rhodospirillum rubrum

Abstract

The CO dehydrogenase from the photosynthetic bacterium R. rubrum was purified > 600-fold by DEAE-cellulose chromatography, heat treatment, hydroxylapatite chromatography and preparative scale gel electrophoresis. In vitro, this enzyme catalyzed a 2-electron oxidation of CO to form CO2 as the product. The reaction was dependent on the addition of an electron acceptor. The enzyme was O2 labile, heat stable and resistant to tryptic and chymotryptic digestion. Optimum in vitro activity occurred at pH 10.0. A sensitive, Hb-based assay for measuring dissolved CO levels is presented. The in vitro Km for CO was determined to be 110 .mu.M. CO, through an unknown mechanism, stimulated H2 evolution in whole cells, suggesting the presence of a reversible dehydrogenase in R. rubrum which is CO insensitive in vivo.