PT  - JOURNAL ARTICLE
AU  - Timothy S. Tracy
AU  - J. Matthew Hutzler
AU  - Robert L. Haining
AU  - Allan E. Rettie
AU  - Matthew A. Hummel
AU  - Leslie J. Dickmann
TI  - Polymorphic Variants (CYP2C9*3 and CYP2C9*5) and the F114L Active Site Mutation of CYP2C9: Effect on Atypical Kinetic Metabolism Profiles
AID  - 10.1124/dmd.30.4.385
DP  - 2002 Apr 01
TA  - Drug Metabolism and Disposition
PG  - 385--390
VI  - 30
IP  - 4
4099  - http://dmd.aspetjournals.org/content/30/4/385.short
4100  - http://dmd.aspetjournals.org/content/30/4/385.full
SO  - Drug Metab Dispos2002 Apr 01; 30
AB  - CYP2C9 wild-type protein has been shown to exhibit atypical kinetic profiles of metabolism that may affect in vitro-in vivo predictions made during the drug development process. Previous work suggests a substrate-dependent effect of polymorphic variants of CYP2C9 on the rate of metabolism; however, it is hypothesized that these active site amino acid changes will affect the kinetic profile of a drug's metabolism as well. To this end, the kinetic profiles of three model CYP2C9 substrates (flurbiprofen, naproxen, and piroxicam) were studied using purified CYP2C9*1 (wild-type) and variants involving active site amino acid changes, including the naturally occurring variants CYP2C9*3 (Leu359) and CYP2C9*5 (Glu360) and the man-made mutant CYP2C9 F114L. CYP2C9*1 (wild-type) metabolized each of the three compounds with a distinctive profile reflective of typical hyperbolic (flurbiprofen), biphasic (naproxen), and substrate inhibition (piroxicam) kinetics. CYP2C9*3 metabolism was again hyperbolic for flurbiprofen, of a linear form for naproxen (no saturation noted), and exhibited substrate inhibition with piroxicam. CYP2C9*5-mediated metabolism was hyperbolic for flurbiprofen and piroxicam but linear with respect to naproxen turnover. The F114L mutant exhibited a hyperbolic kinetic profile for flurbiprofen metabolism, a linear profile for naproxen metabolism, and a substrate inhibition kinetic profile for piroxicam metabolism. In all cases except F114L-mediated piroxicam metabolism, turnover decreased and the Km generally increased for each allelic variant compared with wild-type enzyme. It seems that the kinetic profile of CYP2C9-mediated metabolism is dependent on both substrate and the CYP2C9 allelic variant, thus having potential ramifications on drug disposition predictions made during the development process. The American Society for Pharmacology and Experimental Therapeutics