The cytochrome P-450 dependent monooxygenase system plays a pivotal role in both the detoxification and bioactivation of drugs, environmental contaminants, and other potential chemical toxicants. The balance between detoxification and activation is largely dependent on the relative amounts and activities of different isozymes of cytochrome P-450. The long-term goal of the research proposed in this application is to design irreversible inhibitors of specific isozymes of cytochrome P-450. Such isozyme-specific inhibitors could be used in vivo either 1) diagnostically to assess the tole of the various cytochromes in mediating or protecting against chemical toxicity of 2) therapeutically to redirect the metabolism of xenobiotics from potentially harmful to innocuous pathways. This proposal will focus on determining the mechanism, isozyme selectivity and structural requirements of the suicide inactivation of hepatic cytochromes P-450 by dichloromethyl compounds such as chloramphenicol. Emphasis will first be placed on determining the structural features responsible for the selectivity of chloramphenicol analogs as inactivators of rat liver cytochromes P-450 and on synthesizing specific inhibitors of certain hepatic cytochromes P-450 in the rat and rabbit. Other experiments will be directed towards determining the mechanism by which the heme moiety of the major phenobarbital-inducible isozyme of rat liver cytochrome P-450 is destroyed by certain dichloromethyl compounds. Subsequent studies will focus on assessing the feasibility of using some of the selective inhibitors identified as probes and modulators of the activity of hepatic cytochromes P- 450 in uninduced rats. Finally, the selectivity of chloramphenicol as an inactivator of human liver cytochromes P-450 in vitro will be evaluated. These studies should provide the rational basis for the design of isozyme-specific inhibitors for modulating monooxygenase function in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES003619-06
Application #
3251103
Study Section
Toxicology Subcommittee 2 (TOX)
Project Start
1985-02-01
Project End
1993-01-31
Budget Start
1990-02-01
Budget End
1991-01-31
Support Year
6
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of Arizona
Department
Type
Schools of Pharmacy
DUNS #
City
Tucson
State
AZ
Country
United States
Zip Code
85721
Shah, Manish B; Zhang, Qinghai; Halpert, James R (2018) Crystal Structure of CYP2B6 in Complex with an Efavirenz Analog. Int J Mol Sci 19:
Chen, Chao; Liu, Jingbao; Halpert, James R et al. (2018) Use of Phenoxyaniline Analogues To Generate Biochemical Insights into the Interactio n of Polybrominated Diphenyl Ether with CYP2B Enzymes. Biochemistry 57:817-826
Shah, Manish B; Liu, Jingbao; Zhang, Qinghai et al. (2017) Halogen-? Interactions in the Cytochrome P450 Active Site: Structural Insights into Human CYP2B6 Substrate Selectivity. ACS Chem Biol 12:1204-1210
Shah, Manish B; Jang, Hyun-Hee; Wilderman, P Ross et al. (2016) Effect of detergent binding on cytochrome P450 2B4 structure as analyzed by X-ray crystallography and deuterium-exchange mass spectrometry. Biophys Chem 216:1-8
Liu, Jingbao; Shah, Manish B; Zhang, Qinghai et al. (2016) Coumarin Derivatives as Substrate Probes of Mammalian Cytochromes P450 2B4 and 2B6: Assessing the Importance of 7-Alkoxy Chain Length, Halogen Substitution, and Non-Active Site Mutations. Biochemistry 55:1997-2007
Shah, Manish B; Wilderman, P Ross; Liu, Jingbao et al. (2015) Structural and biophysical characterization of human cytochromes P450 2B6 and 2A6 bound to volatile hydrocarbons: analysis and comparison. Mol Pharmacol 87:649-59
Jang, Hyun-Hee; Liu, Jingbao; Lee, Ga-Young et al. (2015) Functional importance of a peripheral pocket in mammalian cytochrome P450 2B enzymes. Arch Biochem Biophys 584:61-9
Wilderman, P Ross; Jang, Hyun-Hee; Malenke, Jael R et al. (2014) Functional characterization of cytochromes P450 2B from the desert woodrat Neotoma lepida. Toxicol Appl Pharmacol 274:393-401
Jang, Hyun-Hee; Davydov, Dmitri R; Lee, Ga-Young et al. (2014) The role of cytochrome P450 2B6 and 2B4 substrate access channel residues predicted based on crystal structures of the amlodipine complexes. Arch Biochem Biophys 545:100-7
Shah, Manish B; Jang, Hyun-Hee; Zhang, Qinghai et al. (2013) X-ray crystal structure of the cytochrome P450 2B4 active site mutant F297A in complex with clopidogrel: insights into compensatory rearrangements of the binding pocket. Arch Biochem Biophys 530:64-72

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