title: Hydrogen-ubiquinone oxidoreductase activity by the Bradyrhizobium japonicum membrane-bound hydrogenase.
abstract: The Bradyrhizobium japonicum heterodimeric nickel-iron hydrogenase efficiently catalyzed H2-ubiquinone-1 oxidoreductase activity at rates up to 47% of the maximal rates obtained using the artificial electron acceptor methylene blue. Gel filtration chromatography and SDS-polyacrylamide gel electrophoresis experiments demonstrated that the purified enzyme was a heterodimer containing only the 65 kDa and 33 kDa subunits. Reduced minus oxidized absorption difference spectra demonstrated the absence of detectable cytochromes. The H2-ubiquinone-1 oxidoreductase activity of both the purified heterodimeric hydrogenase and membranes was significantly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide and antimycin A, inhibitors known to act in the quinone region of electron transport chains. Our results are the first report of H2-ubiquinone oxidoreductase activity by a purified hydrogenase.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD 21218-2685.
authors.forename: D M
authors.initials: DM
authors.lastname: Ferber
authors.forename: R J
authors.initials: RJ
authors.lastname: Maier
mesh_terms: D000968:Antimycin A / Q000494:pharmacology; D003580:Cytochromes / Q000032:analysis; D004579:Electron Transport; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D006912:Hydroxyquinolines / Q000494:pharmacology; D008566:Membranes / Q000201:enzymology; D008751:Methylene Blue / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D012230:Rhizobiaceae / Q000201:enzymology*; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D003580:Cytochromes; D006912:Hydroxyquinolines; D014451:Ubiquinone; C001333:2-(n-heptyl)-4-hydroxyquinoline N-oxide; D000968:Antimycin A; D006859:Hydrogen; D010088:Oxidoreductases; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D008751:Methylene Blue