Kinetic Studies of Ammonia Monooxygenase Inhibition in Nitrosomonas europaea by Hydrocarbons and Halogenated Hydrocarbons in an Optimized Whole-Cell Assay.

作者: William K Keener , Daniel J Arp , None

DOI: 10.1128/AEM.59.8.2501-2510.1993

关键词: Ammonia monooxygenaseNitrobacteraceaeSubstrate (chemistry)Non-competitive inhibitionHalocarbonChemistryStereochemistryNitrosomonas europaeaAmmoniaHydroxylamine Oxidoreductase

摘要: The inhibitory effects of 15 hydrocarbons and halogenated on NH3 oxidation by ammonia monooxygenase (AMO) in intact cells the nitrifying bacterium Nitrosomonas europaea were determined. Determination AMO activity, measured as NO2- production, required coupling hydroxylamine oxidoreductase (HAO) activity with NH3-dependent NH2OH production AMO. Hydrazine, an alternate substrate for HAO, was added to reaction mixtures a source reductant Most inhibitors exhibited competitive or noncompetitive inhibition patterns. character generally decreased (KiE/KiES increased) molecular size increased. For example, CH4 C2H4 oxidation, whereas remaining alkanes (up C4) monohalogenated (Cl, Br, I) noncompetitive. Oxidation C2H5Br (noncompetitive) increased NH4+ concentration up 40 mM, oxidations (KiE ≪ KiES) diminished at mM NH4+. Multichlorinated compounds produced nonlinear Lineweaver-Burk plots. Iodinated (CH3I, C2H5I) C2Cl4 potent oxidation. Maximum rates NH3, C2H4, C2H6 approximately equivalent, suggesting common rate-determining step. These data support active-site model consisting NH3-binding site second that binds inhibitors, occurring either site.

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