The P450-dependent mixed-function oxidases found in almost all mammalian cells play a critical role in the metabolic activation and detoxication of many chemical carcinogens. The primary goals of the proposed research are to gain a better understanding of the structures of the active sites of several different forms of P450, to : identify the critical amino acid residues involved in the P450 active sites involved in catalysis and substrate binding and to gain a better understanding of the mechanisms by which these enzymes catalyze the reactions involved in the metabolic activation and detoxication of chemical carcinogens and other toxic agents. In order to achieve these goals the specific aims of this research proposal are: 1. To investigate mechanism-based inactivation of cytochromes P450 by 2-ethynylnaphthalene, 9-ethynylphenanthrene, and 7-ethynylcoumarin, to identify the amino acid(s) and peptide(s) at the active site modified during inactivation, and to determine the mechanism by which inactivation occurs; 2. To study the mechanism-based inactivation of cytochromes P450 by N-benzyl-1-aminobenzotriazole in order to identify the modified active site polypeptide(s) and amino acid residue(s) and to determine the mechanism of inactivation; 3. To investigate the mechanism-based inactivation of cytochromes P450 by isothiocyanates and to identify the modified amino acid residue(s) at the active site and to ascertain the catalytic step(s) blocked by the isothiocyanates; 4. To characterize the mechanism-based inactivation of cytochromes P450 by phencyclidine and 2-phenyl-2-(1-piperidynyl)propane, to identify the modified active site peptide(s) and amino acid residue(s) and the catalytic steps blocked by the inactivation; and 5. To investigate the mechanism-based inactivation of cytochromes P450 by 17-a-ethynylestradiole, to identify the modified active site polypeptide(s) and amino acid residue(s) and to determine the mechanism of inactivation. Studies aimed at investigating the effect of the various mechanism-based inactivators on the topology of the active sites of these P450s will also be investigated. Site-specific mutagenesis of active site residues modified by the : mechanism-based inactivators will also be used to determine the roles of these residues in catalysis. The identification of critical amino acid residues involved in catalysis and the determination of their specific roles in P450-catalyzed reactions will prove to be extremely valuable for developing approaches for selectively modulating the catalytic activity of these enzymes. Results of the these studies could provide information that will be extremely valuable in developing methods to decrease the risk of developing cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA016954-31
Application #
6889933
Study Section
Chemical Pathology Study Section (CPA)
Program Officer
Johnson, Ronald L
Project Start
1981-09-01
Project End
2007-09-20
Budget Start
2005-05-01
Budget End
2007-09-20
Support Year
31
Fiscal Year
2005
Total Cost
$381,737
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Pharmacology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Lin, Hsia-Lien; Zhang, Haoming; Hollenberg, Paul F (2018) Formation of Both Heme and Apoprotein Adducts Contributes to the Mechanism-Based Inactivation of Human CYP2J2 by 17?-Ethynylestradiol. Drug Metab Dispos 46:813-822
Lin, Hsia-Lien; Zhang, Haoming; Walker, Vyvyca J et al. (2017) Heme Modification Contributes to the Mechanism-Based Inactivation of Human Cytochrome P450 2J2 by Two Terminal Acetylenic Compounds. Drug Metab Dispos 45:990-999
Lin, Hsia-Lien; Zhang, Haoming; Kenaan, Cesar et al. (2016) Roles of Residues F206 and V367 in Human CYP2B6: Effects of Mutations on Androgen Hydroxylation, Mechanism-Based Inactivation, and Reversible Inhibition. Drug Metab Dispos 44:1771-1779
Walker, Vyvyca J; Griffin, Alisha P; Hammar, Dagan K et al. (2016) Metabolism of Anandamide by Human Cytochrome P450 2J2 in the Reconstituted System and Human Intestinal Microsomes. J Pharmacol Exp Ther 357:537-44
Snider, Natasha T; Walker, Vyvyca J; Hollenberg, Paul F (2016) Assay of Endocannabinoid Oxidation by Cytochrome P450. Methods Mol Biol 1412:227-36
D'Agostino, Jaime; Zhang, Haoming; Kenaan, Cesar et al. (2015) Mechanism-Based Inactivation of Human Cytochrome P450 2B6 by Chlorpyrifos. Chem Res Toxicol 28:1484-95
Calinski, Diane M; Zhang, Haoming; Ludeman, Susan et al. (2015) Hydroxylation and N-dechloroethylation of Ifosfamide and deuterated Ifosfamide by the human cytochrome p450s and their commonly occurring polymorphisms. Drug Metab Dispos 43:1084-90
Zhang, Haoming; Lauver, D Adam; Lucchesi, Benedict R et al. (2013) Formation, reactivity, and antiplatelet activity of mixed disulfide conjugates of clopidogrel. Mol Pharmacol 83:848-56
Zhang, Haoming; Gay, Sean C; Shah, Manish et al. (2013) Potent mechanism-based inactivation of cytochrome P450 2B4 by 9-ethynylphenanthrene: implications for allosteric modulation of cytochrome P450 catalysis. Biochemistry 52:355-64
Sridar, Chitra; Hanna, Imad; Hollenberg, Paul F (2013) Quantitation of UGT1A1 in human liver microsomes using stable isotope-labelled peptides and mass spectrometry based proteomic approaches. Xenobiotica 43:336-45

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