title: Ammonia oxidation by Nitrosomonas eutropha with NO(2) as oxidant is not inhibited by acetylene.
abstract: The effect of acetylene ((14)C(2)H(2)) on aerobic and anaerobic ammonia oxidation by Nitrosomonas eutropha was investigated. Ammonia monooxygenase (AMO) was inhibited and a 27 kDa polypeptide (AmoA) was labelled during aerobic ammonia oxidation. In contrast, anaerobic, NO(2)-dependent ammonia oxidation (NO(2)/N(2)O(4) as oxidant) was not affected by acetylene. Further studies gave evidence that the inhibition as well as the labelling reaction were O(2)-dependent. Cells pretreated with acetylene under oxic conditions were unable to oxidize ammonia with O(2) as oxidant. After these cell suspensions were supplemented with gaseous NO(2), ammonia oxidation activity of about 140 micromol NH(4)(+) (g protein)(-1) h(-1) was detectable under both oxic and anoxic conditions. A significantly reduced acetylene inhibition of the ammonia oxidation activity was observed for cells incubated in the presence of NO. This suggests that NO and acetylene compete for the same binding site on AMO. On the basis of these results a new hypothetical model of ammonia oxidation by N. eutropha was developed.
authors.affiliation: Department of Microbiology, University of Nijmegen, Toernooidveld 1, 6525 ED Nijmegen, The Netherlands1.
authors.forename: Ingo
authors.initials: I
authors.lastname: Schmidt
authors.affiliation: Institute for General Botany, Department of Microbiology, University of Hamburg, Ohnhorststraße 18, 22609 Hamburg, Germany2.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Bock
authors.affiliation: Department of Microbiology, University of Nijmegen, Toernooidveld 1, 6525 ED Nijmegen, The Netherlands1.
authors.forename: Mike S M
authors.initials: MSM
authors.lastname: Jetten
mesh_terms: D000114:Acetylene / Q000494:pharmacology*; D000332:Aerobiosis; D000641:Ammonia / Q000378:metabolism*; D000693:Anaerobiosis; D000818:Animals; D002417:Cattle; D009585:Nitrogen Dioxide / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000494:pharmacology; D009606:Nitrosomonas / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D009589:Nitrogen Oxides; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D000114:Acetylene; D009585:Nitrogen Dioxide