title: Characterization of two different 2-oxoglutarate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus TK-6.
abstract: A thermophilic, chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, fixes carbon dioxide via the reductive TCA cycle. 2-Oxoglutarate:ferredoxin oxidoreductase (OGOR) is one of the key enzymes of this cycle. Strain TK-6 has two distinct OGOR enzymes termed For and Kor. These enzymes were purified and characterized following heterologous expression in Escherichia coli. The specific activity of For was approximately one-tenth of that of Kor. Additionally, For showed higher thermo-stability than Kor under both aerobic and anaerobic conditions. Western blot analysis showed that both of For and Kor were expressed when strain TK-6 was grown under aerobic conditions. In contrast, only Kor was expressed when the strain was grown under anaerobic conditions using nitrate as a terminal electron acceptor. These results indicate that For supports the optimal growth of strain TK-6 in the presence of oxygen.
authors.affiliation: Department of Biotechnology, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, 113-8657, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000201:enzymology*; D001420:Bacteria, Aerobic / Q000737:chemistry / Q000201:enzymology; D001421:Bacteria, Anaerobic / Q000737:chemistry / Q000378:metabolism; D002952:Citric Acid Cycle / Q000502:physiology; D004789:Enzyme Activation; D004795:Enzyme Stability; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007658:Ketone Oxidoreductases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature
chemical_list: D011994:Recombinant Proteins; D007658:Ketone Oxidoreductases; C023096:2-oxoglutarate synthase