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KMID : 0893320000150040139
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Journal of Environmental Toxicology
2000 Volume.15 No. 4 p.139 ~ p.145
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Substrate Specificity of the Human Flavin-containing Monooxygenase for Organic Selenium Compounds
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Kim Young-Mi
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Abstract
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The Flavin-containing monooxygenase (FMOs) (EC1.14.13.8) are NADPH-dependent 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 insect cells for catalytic studies. Six commercially available organic selenium compounds were examined for substrate activity with microsomes isolated from Spodoptera frugiperda (Sf)9 cells infected with human FMO3 recombinant baculovirus. While none of the aromatic heterocyclic selenides tested showed detectable activity, all dialkyl- and alkylaryl-selenides free from ionic groups catalyzed the NADPH- and O-dependent oxidation. Kinetic constants demonstrate that (based on Km) dialkyl-and alkylaryl- selenides are better substrates for human FMO3 than analogous nitrogen or sulfur compounds .
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KEYWORD
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Flavin-containing monooxygenase, selenium compounds, baculovirus
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