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Published on: March 28, 2017
Polymorphisms of CYP2C8 Alter First-Electron Transfer Kinetics and Increase Catalytic Uncoupling
William R Arnold1, Susan Zelasko2, Daryl D Meling3
1Department of Biochemistry, University of Illinois Urbana-Champaign, 3813 Veterinary Medicine Basic Sciences Building, 2001 South Lincoln Avenue, Urbana, IL 61802, USA. william.arnold@ucsf.edu.
Genetic variations in Cytochrome P450 2C8 (CYP2C8) alter paclitaxel metabolism by increasing uncoupling and hydrogen peroxide production. These CYP2C8 polymorphisms disrupt electron transfer with cytochrome P450 reductase (CPR).
Area of Science:
- Biochemistry
- Pharmacology
- Enzymology
Background:
- Cytochrome P450 2C8 (CYP2C8) is a key enzyme metabolizing numerous drugs, including paclitaxel (PAC).
- Naturally occurring CYP2C8 polymorphisms (*2 and *3) affect paclitaxel hydroxylation rates without active site mutations.
Purpose of the Study:
- To investigate the mechanism by which CYP2C8 polymorphisms (*2, *3) alter paclitaxel metabolism.
- To determine the impact of these polymorphisms on enzyme uncoupling and redox interactions.
Main Methods:
- Anaerobic stopped-flow spectroscopy was employed to measure electron transfer kinetics.
- Analysis focused on hydrogen peroxide formation during paclitaxel turnover.
Main Results:
- CYP2C8*2 and *3 polymorphisms increase the uncoupling of paclitaxel metabolism, leading to higher hydrogen peroxide generation per turnover.
- Altered first electron transfer kinetics were observed, indicating disfavored electron transfer from cytochrome P450 reductase (CPR).
Conclusions:
- CYP2C8 polymorphisms significantly impact the enzyme's catalytic cycle.
- These genetic variations disrupt essential redox interactions between CYP2C8 and CPR, affecting drug metabolism.
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