PMID:16349014

Citation	Keener, WK and Arp, DJ (1993) Kinetic Studies of Ammonia Monooxygenase Inhibition in Nitrosomonas europaea by Hydrocarbons and Halogenated Hydrocarbons in an Optimized Whole-Cell Assay. Appl. Environ. Microbiol. 59:2501-10
Abstract	The inhibitory effects of 15 hydrocarbons and halogenated hydrocarbons on NH(3) oxidation by ammonia monooxygenase (AMO) in intact cells of the nitrifying bacterium Nitrosomonas europaea were determined. Determination of AMO activity, measured as NO(2) production, required coupling of hydroxylamine oxidoreductase (HAO) activity with NH(3)-dependent NH(2)OH production by AMO. Hydrazine, an alternate substrate for HAO, was added to the reaction mixtures as a source of reductant for AMO. Most inhibitors exhibited competitive or noncompetitive inhibition patterns. The competitive character generally decreased (K(i) (E)/K(i) (ES) increased) as the molecular size of the inhibitors increased. For example, CH(4) and C(2)H(4) were competitive inhibitors of NH(3) oxidation, whereas the remaining alkanes (up to C(4)) and monohalogenated (Cl, Br, I) alkanes were noncompetitive. Oxidation of C(2)H(5)Br (noncompetitive) increased as the NH(4) concentration increased up to 40 mM, whereas oxidations of inhibitors with competitive character (K(i) (E) < K(i) (ES)) were diminished at 40 mM NH(4). Multichlorinated compounds produced nonlinear Lineweaver-Burk plots. Iodinated alkanes (CH(3)I, C(2)H(5)I) and C(2)Cl(4) were potent inhibitors of NH(3) oxidation. Maximum rates of NH(3), C(2)H(4), and C(2)H(6) oxidations were approximately equivalent, suggesting a common rate-determining step. These data support an active-site model for AMO consisting of an NH(3)-binding site and a second site that binds noncompetitive inhibitors, with oxidation occurring at either site.
Links	PubMed PMC182312
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
NITEU:AMOA	enables	GO:0004497: monooxygenase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
NITEU:AMOA		GO:0004497: monooxygenase activity	ECO:0000314:		F		Table 1	complete CACAO 2227

References

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