title: Human cytochrome p450 enzymes of importance for the bioactivation of methyleugenol to the proximate carcinogen 1'-hydroxymethyleugenol.
abstract: In vitro studies were performed to elucidate the human cytochrome P450 enzymes involved in the bioactivation of methyleugenol to its proximate carcinogen 1'-hydroxymethyleugenol. Incubations with Supersomes, expressing individual P450 enzymes to a high level, revealed that P450 1A2, 2A6, 2C9, 2C19, and 2D6 are intrinsically able to 1'-hydroxylate methyleugenol. An additional experiment with Gentest microsomes, expressing the same individual enzymes to roughly average liver levels, indicated that P450 1A2, 2C9, 2C19, and 2D6 contribute to methyleugenol 1'-hydroxylation in the human liver. A study, in which correlations between methyleugenol 1'-hydroxylation in human liver microsomes from 15 individuals and the conversion of enzyme specific substrates by the same microsomes were investigated, showed that P450 1A2 and P450 2C9 are important enzymes in the bioactivation of methyleugenol. This was confirmed in an inhibition study in which pooled human liver microsomes were incubated with methyleugenol in the presence and absence of enzyme specific inhibitors. Kinetic studies revealed that at physiologically relevant concentrations of methyleugenol P450 1A2 is the most important enzyme for bioactivation of methyleugenol in the human liver showing an enzyme efficiency (kcat/Km) that is approximately 30, 50, and > 50 times higher than the enzyme efficiencies of, respectively, P450 2C9, 2C19, and 2D6. Only when relatively higher methyleugenol concentrations are present P450 2C9 and P450 2C19 might contribute as well to the bioactivation of methyleugenol in the human liver. A 5-fold difference in activities was found between the 15 human liver microsomes of the correlation study (range, 0.89-4.30 nmol min(-1) nmol P450(-1)). Therefore, interindividual differences might cause variation in sensitivity toward methyleugenol. Especially lifestyle factors such as smoking (induces P450 1A) and the use of barbiturates (induces P450 2C) can increase the susceptibility for adverse effects of methyleugenol.
authors.affiliation: Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen, The Netherlands. suzanne.jeurissen@wur.nl
authors.forename: Suzanne M F
authors.initials: SM
authors.lastname: Jeurissen
authors.forename: Jan J P
authors.initials: JJ
authors.lastname: Bogaards
authors.forename: Marelle G
authors.initials: MG
authors.lastname: Boersma
authors.forename: Judith P F
authors.initials: JP
authors.lastname: ter Horst
authors.forename: Hanem M
authors.initials: HM
authors.lastname: Awad
authors.forename: Yiannis C
authors.initials: YC
authors.lastname: Fiamegos
authors.forename: Teris A
authors.initials: TA
authors.lastname: van Beek
authors.forename: Gerrit M
authors.initials: GM
authors.lastname: Alink
authors.forename: Ernst J R
authors.initials: EJ
authors.lastname: Sudhölter
authors.forename: Nicole H P
authors.initials: NH
authors.lastname: Cnubben
authors.forename: Ivonne M C M
authors.initials: IM
authors.lastname: Rietjens
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001571:Benzoflavones / Q000494:pharmacology; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002460:Cell Line; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D065731:Cytochrome P-450 CYP2C19; D065729:Cytochrome P-450 CYP2C9; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005054:Eugenol / Q000031:analogs & derivatives* / Q000378:metabolism; D005421:Flavoring Agents / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D006899:Mixed Function Oxygenases; D011994:Recombinant Proteins / Q000378:metabolism; D018570:Risk Assessment; D013426:Sulfaphenazole / Q000494:pharmacology
chemical_list: D001571:Benzoflavones; D002273:Carcinogens; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D005421:Flavoring Agents; D011994:Recombinant Proteins; D013426:Sulfaphenazole; C005223:methyleugenol; D005054:Eugenol; C011512:alpha-naphthoflavone; D003577:Cytochrome P-450 Enzyme System; C108731:1'-(hydroxymethyl)eugenol; D006899:Mixed Function Oxygenases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D019388:Cytochrome P-450 CYP1A2; D065731:Cytochrome P-450 CYP2C19