title: Electron transfer during the oxidation of ammonia by the chemolithotrophic bacterium Nitrosomonas europaea.
abstract: The combined action of ammonia monooxygenase, AMO, (NH(3)+2e(-)+O(2)-->NH(2)OH) and hydroxylamine oxidoreductase, HAO, (NH(2)OH+H(2)O-->HNO(2)+4e(-)+4H(+)) accounts for ammonia oxidation in Nitrosomonas europaea. Pathways for electrons from HAO to O(2), nitrite, NO, H(2)O(2) or AMO are reviewed and some recent advances described. The membrane cytochrome c(M)552 is proposed to participate in the path between HAO and ubiquinone. A bc(1) complex is shown to mediate between ubiquinol and the terminal oxidase and is shown to be downstream of HAO. A novel, red, low-potential, periplasmic copper protein, nitrosocyanin, is introduced. Possible mechanisms for the inhibition of ammonia oxidation in cells by protonophores are summarized. Genes for nitrite- and NO-reductase but not N(2)O or nitrate reductase are present in the genome of Nitrosomonas. Nitrite reductase is not repressed by growth on O(2); the flux of nitrite reduction is controlled at the substrate level.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: M
authors.initials: M
authors.lastname: Whittaker
authors.forename: D
authors.initials: D
authors.lastname: Bergmann
authors.forename: D
authors.initials: D
authors.lastname: Arciero
authors.forename: A B
authors.initials: AB
authors.lastname: Hooper
mesh_terms: D000595:Amino Acid Sequence; D000641:Ammonia / Q000737:chemistry* / Q000378:metabolism; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009573:Nitrites / Q000737:chemistry; D009606:Nitrosomonas / Q000378:metabolism* / Q000648:ultrastructure; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011522:Protons; D014451:Ubiquinone / Q000737:chemistry
chemical_list: D003574:Cytochrome c Group; D009573:Nitrites; D011522:Protons; C083951:cytochrome c553; D014451:Ubiquinone; D006418:Heme; D000641:Ammonia; C022302:cytochrome C-552; D010088:Oxidoreductases; C021401:hydroxylamine dehydrogenase; C045582:ammonia monooxygenase; D014450:Electron Transport Complex III