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KMID : 0893320010160020097
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Journal of Environmental Toxicology
2001 Volume.16 No. 2 p.97 ~ p.102
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Effect of Substrate Size on Activities of Thiocarbamides with the Human Flavin-containing Monooxygenase 3
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Kim Young-Mee
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Abstract
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The flavin-containing monooxygenases(FMOs) (EC1.14.13.8) are NADPH0dependent flavoenzymes that catalyze oxidation of soft nucleophilic heteroatom centers in a range of structurally diverse compounds, including foods, drugs, pesticides, and other xenobiotics. In humans, FMO3 is quantitatively a major human liver monooxygenase. In the present study, the baculovirus expression vector system was used to overexpress human FMO3 in sect cells for stalytic studies. Microsomes isolated from Spodoptera frugiperda(Sf)9 cells infected with human FMO3 recombinant baculovirus catalyzed the NADPH-and O-dependent oxidation of methimazole, thiourea, and phenylthiourea. However there was no detectable activity with 1, 3-diphenylthiourea or larger thiocarbamides. Microsomes from control Sf9 cells were devoid of methimazole or thiourea S-oxygenase activity. 1, 3-diphenylthiourea is apparently completely excluded from the catalytic site, these amines drugs are probably approaching the upper size limits of xenobiotics accepted by human FMO3. The substrate specificity of this iosform in humans appears considerably more restriceted than that of pig, guinea pig, rat or rabbit FMO3.
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KEYWORD
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flavin-containing monooxygenase, thiocarbamides, baculovirus
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