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Characterization of Methimazole Metabolism by Mouse Fmo1, 2 and 3: Determination of Enzyme Co‐expression
Author(s) -
VanDyke Jonathan Edward,
Krueger Sharon K,
Siddens Lisbeth K,
Henderson Marilyn C,
Ban David T,
Williams David E
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a261-d
Subject(s) - gene isoform , monooxygenase , enzyme , biochemistry , metabolism , chemistry , flavin containing monooxygenase , sodium cholate , enzyme assay , biology , microbiology and biotechnology , cytochrome p450 , gene
Flavin‐containing monooxygenases (FMOs) efficiently catalyze oxidation of chemicals such as thioureas and thioethers. Enzyme activities of baculovirus‐expressed mouse Fmo isoforms were characterized in order to discriminate FMOs co‐expressed in mouse tissues. We hypothesized that if the activity of each isoform could be determined under two sets of conditions and isoforms are uniquely discriminated by the second set of conditions, the contribution of individual isoforms from mouse tissues expressing multiple Fmos could be mathematically determined. Metabolism of 2.0 mM methimazole by expressed mouse Fmo1, 2 and 3 was measured at pH 8.5 to determine the activity (nmol·min‐1·nmol‐1) of each isoform under standard conditions. Mixtures of expressed Fmos were prepared and predictions of combined activity made and compared with observed activity. Activity of individual Fmos was also monitored with sodium cholate at a concentration of 1%. Under standard conditions, mixtures performed as expected (e.g. observed change in activity was the combined change of Fmos assayed individually). After addition of cholate, Fmo1, Fmo2 and Fmo3 retained 26%, 103% and 45% activity, respectively. Since all Fmos were distinguishable with cholate it was possible to develop mathematical equations for simultaneous co‐determination of all three isoforms. We are confirming our model with expressed isoforms and will apply this model to mouse tissues. Supported by PHS grant HL038650.