Toxicological Research

Korean Society of Toxicology & Korea Environmental Mutagen Society (한국독성학회)
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The Effect of Dehydronifedipine on the Oxidation of Aflatoxin $B_1$ by Cytochrome P450 3A4

Cytochrome P450 3A4에 의한 Aflatoxin $B_1$의 산화에 대한 Dehydronifedipine의 영향

  • 김복량 (원광대학교 의과대학 생화학교실) ;
  • 권강범 (한의과대학 생리학교실) ;
  • 김동현 (한국과학기술연구원 생체대사연구센터)
  • Published : 1999.03.01
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Abstract

Cytochrome P450 (CYP) 3A4 metabolizes aflatoxin B1 (AFB1) to AFB1-exo-8,9-epoxide (8,9-epoxidation) and aflatoxin Q1 (AFQ1; 3$\alpha$-hydroxylation) simultaneously. We investigated whether each metabolite was formed via its own binding site of CAP3A4 active site. Kinetics of the formation of the two metabolites were sigmoidal and consistent with the kinetics of substrate activation. The HIll model predicted that two substrate binding wites are involved in the oxidationof AFB1 by CYP3A4. Dehydronifedipine, a metabolite of nifedipine generated by CYP3A4, inhibited the formation of AFQ1 without any inhibition in the formation of AFB1-exo-8,9-epoxidation. Dehydronifedipine was found to act as a reversible competitive inhibitor against 3$\alpha$-hydroxylation of AFB1. Vmax and S0.5 of the 8,9-epoxidation were not changed in the presence of 0, 50, or 100 $\mu\textrm{M}$ dehydronifedipine. S0.5 of 3$\alpha$-hydroxylation was increased from 58$\pm$4 $\mu\textrm{M}$ to 111$\pm$8 $\mu\textrm{M}$ in the presence of 100 $\mu\textrm{M}$ nifedipine whereas Vmax was not changed. These results suggest that there exist two independent binding sites in the active site of CAP3A4 . One binding site is responsible for AFB1-exo-8,9-epoxidation and the other is involved in 3$\alpha$-hydroxylation of AFB1. Dehydronifedipine might selectively bind to the site which is responsible for the formation of AFQ1 in the active site of CYP3A4.

Keywords

References

  1. JPM v.29 The use of vitro metabolism studies in the understanding of new drugs Chiu, L.
  2. Toxicol. Appl. Pharmacol. v.141 The kinetics of aflatoxin B₁ oxidation by human cDNA-expressed and human liver microsomla cytochromes P450 1A2 and 3A4 Gallagher, E.P.;Kunze, K.L.;Stapleton, P.L.;Eaton, D.L.
  3. Arch. Biochem. Biophys. v.305 Expression of modified human cytochrome P450 3A4 in Escherichia coli and purification and reconstitution of the enzyme Gillam, E.M.J.;Baba, T.;Kim, B.R.;Ohmori, S.;Guengerich, F.P.
  4. Arch. Biochem. Biophys. v.205 Purification of cytochrome epoxide hydratase from a single preparation of rat liver microsomes Guengerich, F.P.;Martin, M.V.
  5. J. Biol. Chem. v.261 CHaracterzation of rat and human liver microsomal cytochrome P450 forms involved in nifedipine oxidation, a prottype for genetic polymorphism in oxidative drug metabolism Guengerich, F.P.;Martin, M.V.;Beaune, P.H.;Kremers, P.;Wolff, T.;Waxman, D.J.
  6. Chem. Res. Toxicol. v.3 Mechanism-based inactivation of human liver cytochrome P-450 3A4 by gestodene Guengerich, F.P.
  7. Life Sci. v.50 Minireview: Human cytochrome P-450 enzymes Guengerich, F.P.
  8. Proceedings, 8th Int. confernece on cytochrome P450: Biochemistry, Biophysics, and Molecular Biology Mechanism of enhancement and inhition of cytochrome P450 catalytic activities Guengerich, F.P.;Kim, B.R.;Gillam, E.M.J.;Shimada, T.;Lechner MC(ed.)
  9. Cancer Res. v.54 Metabolism of taxol Participation of cytochrome P450 3A4 and of an unknown P450 enzyme Harris, J.W.;Rahman, A.;Kim, B.R.;Guenerich, F.P.;Collins, J.M.
  10. Anesth. Analg. v.76 Human alfentanil metabolism by cytochrome P450 3A3/4, An explanatio for interindividual variability in alfentanil clearance? Kharasch, E.D.;Thummel, K.E.
  11. Biochem. Biophys. Res. Commun. v.242 Influence of glu tathione on the catality of reconstituted cytochrome P450 3A4 Kim, B.R.;Kim, D.H.
  12. Biochem. Mol. Biol. Int. v.43 Differential inhibition of aflatoxin B₁ oxidation by gestodene action on human liver microsomes Kim, B.R.;Oh, H.S.;Kim, D.H.
  13. Korean J. Toxicol. v.11 Reaction mechanism of troleandomycin on the activity of human liver microsomal cytochrome P450 3A4 Kim, B.R.;Oh, H.S.;Kim, H.J.
  14. Antimicrobial Agents Chemother. v.37 Cytochrome P450 complex formation by dirithromycin and other macrolides in rat and human livers Lindstrom, T.D.;Hanssen, B.R.;Wrighton, S.A.
  15. DNA Cell Biol. v.12 The P450 superfamily: Update on new sequences, gene mapping, accession numbers, darly trivial names of enzymes, and nomenclature Nelson, D.R.;Kamataki, T.;Waxman, D.J.;Guengerich, F.P.;Estabrook, R.W.;Feyereisen, R.;Gonzalez, F.J.;Coon, M.J.;Gunsalus, I.C.;Gotoh, O.;Okuda, K.;Nebert, D.W.
  16. Korean J. Toxicol. v.11 Effects of several inhibitos of human liver microsomal cytochrome P450 3A4 on catalytic activities of the enzyme Oh, H.S.;Lee, K.S.;Kim, B.R.
  17. Biotransformation of xenobiotics in Toxicology Parkinson, A.;Klaassen, C.D.(ed.)
  18. Biochem, Pharmacol. v.44 The effect of enzyme induction on the cytochrome P450-mediated bioactivation of carbazepine by mouse liver microsomes Pirmohamed, M.;Neil R. Kitteringham.;Breckenridge, A.M.;Park, B.K.
  19. Chem. Res. Toxicol. v.5 Oxidation of aflatoxins and sterigmatocystin by human liver microsomes: Signiflcane of aflatoxin Q₁ as a detoxification product of aflatoxin B₁ Raney, K.D.;Shimada, T.;Kim, D.H.;Groopman, J.D.;Harris, T.M.;Guengerich, F.P.
  20. Enzyme kinetics Segel, I,H.
  21. J. Biol. Chem. v.261 Human liver microsomal cytochrome P450 mephenyltoin 4-hydroxylase, a prototype of genetic polymorphism in oxidative drug metabolism. Purification and characterization of two similar forms involved in the reaction Shimada, T.;Misono, K.S.;Guengerich, F.P.
  22. Biochemistry v.33 Activation of CYP3A4: Evidence for the Simultaneous binding of two substrate in a Cytochrome P450 active site Shou, M.J.;Grogan;J.A., Mancewicz;K.W. Krause;F.J. Gonzalez;H.V. Gelboin;K.R. Korzekwa
  23. Biochemistry v.36 Cooperativity in oxidations catalyzed by cytochrome P450 3A4 Ueng, Y.F.;Kuwabara T.;Chun Y.J.;Guengerich F.P.