title: A thermostable NADH oxidase from anaerobic extreme thermophiles.
abstract: A high-abundance NADH-oxidizing enzyme (NADH: acceptor oxidoreductase, EC 1.6.99.3) has been identified and isolated from a range of anaerobic extreme thermophiles, including strains of Clostridium thermohydrosulfuricum and Thermoanaerobium brockii. By use of a pseudo-affinity salt-promoted adsorbent, a nearly pure sample was obtained in one step; remaining impurities were separated by ion-exchange. The fully active purified enzyme contains FAD (two molecules per subunit of 75-78 kDa) and iron-sulphur, and is hexameric in its most active form. The reaction with oxygen is a one- or two-electron transfer to produce superoxide radical and H2O2; other acceptors include tetrazolium salts, dichlorophenol-indophenol, menadione and ferricyanide. The role of the enzyme is not clear; it was found not to be NAD:ferredoxin oxidoreductase, which is a major NADH-utilizing enzyme in these organisms.
authors.affiliation: Centre for Protein and Enzyme Technology, La Trobe University, Bundoora, Vic., Australia.
authors.forename: K
authors.initials: K
authors.lastname: Maeda
authors.forename: K
authors.initials: K
authors.lastname: Truscott
authors.forename: X L
authors.initials: XL
authors.lastname: Liu
authors.forename: R K
authors.initials: RK
authors.lastname: Scopes
mesh_terms: D002850:Chromatography, Gel; D003013:Clostridium / Q000201:enzymology*; D004795:Enzyme Stability; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005415:Flavins / Q000378:metabolism; D016987:Gram-Positive Rods / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*
chemical_list: D005415:Flavins; D009097:Multienzyme Complexes; D005182:Flavin-Adenine Dinucleotide; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases