Formation of a quinoneimine intermediate of 4-fluoro-N-methylaniline by FMO1: carbon oxidation plus defluorination.
Here, we report on the mechanism by which flavin-containing monooxygenase 1 (FMO1) mediates the formation of a reactive intermediate of 4-fluoro-N-methylaniline. FMO1 catalyzed a carbon oxidation reaction coupled with defluorination that led to the formation of 4-N-methylaminophenol, which was a reaction first reported by Boersma et al. (Boersma et al. (1993) Drug Metab. Dispos. 21 , 218 - 230). We propose that a labile 1-fluoro-4-(methylimino)cyclohexa-2,5-dienol intermediate was formed leading to an electrophilic quinoneimine intermediate. The identification of N-acetylcysteine adducts by LC-MS/MS and NMR further supports the formation of a quinoneimine intermediate. Incubations containing stable labeled oxygen (H(2)(18)O or (18)O(2)) and ab initio calculations were performed to support the proposed reaction mechanism.
Driscoll
James P
JP
Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., South San Francisco, California 94080, USA. Driscoll.James@gene.com
Aliagas
Ignacio
I
Harris
Jennifer J
JJ
Halladay
Jason S
JS
Khatib-Shahidi
Sheerin
S
Deese
Alan
A
Segraves
Nathaniel
N
Khojasteh-Bakht
S Cyrus
SC
D000111:Acetylcysteine / Q000737:chemistry; D000627:Aminophenols; D000814:Aniline Compounds / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D002244:Carbon / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D007553:Isotope Labeling; D010084:Oxidation-Reduction; D010103:Oxygen Isotopes; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010636:Phenols / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
D000627:Aminophenols; D000814:Aniline Compounds; D010103:Oxygen Isotopes; D010636:Phenols; D020033:Protein Isoforms; D011994:Recombinant Proteins; C014112:N-methyl-4-aminophenol; C081015:4-fluoro-N-methylaniline; D002244:Carbon; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D000111:Acetylcysteine