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Biodehalogenation: Rapid oxidative metabolism of mono‐ and polyhalomethanes by Methylosinus trichosporium OB‐3b
Author(s) -
Bartnicki E.W.,
Castro C.E.
Publication year - 1994
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620130208
Subject(s) - chemistry , medicinal chemistry , bromide , halogenation , methyl iodide , methane monooxygenase , halide , methyl formate , chloride , inorganic chemistry , nuclear chemistry , organic chemistry , methane , methanol
Resting cells of Methylosinus trichosporium OB‐3b grown in the absence of copper salts rapidly oxidize mono‐ and polyhalomethanes. The order of reactivity of the series is CH 3 X > CH 2 X 2 ≥ CHX 3 (X = CI, Br). Based on halide ion release, the half‐life for methyl bromide and methyl chloride is 9.4 min with a cell density of 0.1 g/ml. The dihalomethanes and bromo‐form react at the same rate and half as rapidly as the methyl halides. Chloroform is converted to carbon dioxide at one‐fourth the methyl halide rate ( t 1/2 = 38 min). No isotope effect was observed with either deuteromethylene chloride or deuterochloro‐form (CD 2 Cl 2 , CDCl 3 ). In all cases, the dehalogenation chemically follows an oxygen insertion into the CH bond, and the final product is carbon dioxide (HCO 3 − ). All reactions are inhibited by acetylene, establishing methane monooxygenase as the responsible enzyme. Incubations with 13 CHCl 3 , 13 CH 2 Br 2 , and 13 CH 3 Br and nuclear magnetic resonance (NMR) analysis of reaction mixtures showed the first hydrolytically stable products from CHCl 3 (HCO 3 − ) and CH 2 Br 2 (CO), but neither formaldehyde nor formate could be detected as intermediates with methyl bromide by this method. The oxidative destruction of halo‐methanes by this methylotroph is rapid and not very sensitive to structure.