Suicidal inactivation and labelling of ammonia mono-oxygenase by acetylene.
Acetylene brings about a progressive inactivation of ammonia mono-oxygenase, the ammonia-oxidizing enzyme in Nitrosomonas europaea. High NH4+ ion concentrations were protective. The inactivation followed first-order kinetics, with a rate constant of 1.5 min-1 at saturating concentrations of acetylene. If acetylene was added in the absence of O2, the cells remained active until O2 was re-introduced. A protective effect was also demonstrated with thiourea, a reversible non-competitive inhibitor of ammonia oxidation. Incubation of cells with [14C]acetylene was found to cause labelling of a single membrane polypeptide. This ran on dodecyl sulphate/polyacrylamide-gel electrophoresis with an Mr value of 28 000. It is concluded that acetylene is a suicide substrate for the mono-oxygenase. The labelling experiment provides the first identification of a constituent polypeptide of ammonia mono-oxygenase.
D000114:Acetylene / Q000031:analogs & derivatives / Q000494:pharmacology*; D000641:Ammonia / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D009606:Nitrosomonas / Q000187:drug effects / Q000201:enzymology*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D010100:Oxygen / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis
D010446:Peptide Fragments; C044736:phenylacetylene; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D000114:Acetylene; D010100:Oxygen