In-vitro and in-vivo effects of the CYP2C9*11 polymorphism on warfarin metabolism and dose

Pharmacogenet Genomics. 2005 Jul;15(7):475-81. doi: 10.1097/01.fpc.0000162005.80857.98.

Abstract

Objective: To determine the in-vitro and in-vivo effects of the CYP2C9*11 polymorphism on (S)-warfarin metabolism.

Methods and results: The *11 allele that results in mutation of Arg335-->Trp occurred with a frequency of approximately 1% in Caucasian and African-American populations. Four subjects carrying the *1/*11 genotype were identified in a clinical cohort of 192 warfarin patients. Compared to control subjects with the *1/*11 genotype (n=127), the *1/*11 group exhibited a 33% reduction in warfarin maintenance dose, that was independent of study population age or INR. In-vitro studies directed towards understanding the mechanism of reduced in-vivo activity revealed very low levels of holo-CYP2C9.11 expression in insect cells and decreased solubility in the presence of detergent. Membrane preparations of CYP2C9.11 contained inactive P420 and exhibited a shorter half-life for thermally induced conversion of P450 to P420 than CYP2C9.1. Metabolic studies demonstrated that functional CYP2C9.11 possessed similar (S)-warfarin hydroxylation regioselectivity and modestly reduced catalytic efficiency relative to the wild-type enzyme.

Conclusions: In-vivo reduction in CYP2C9 (S)-warfarin activity due to the CYP2C9*11 polymorphism may largely be a consequence of decreased enzyme stability resulting in compromised expression of holo-enzyme. Increased enzyme lability of CYP2C9.11 may be related to improper folding due to the disruption of conserved salt-bridge and hydrogen bonding contacts in the loop region between the J and J' helices of the protein.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anticoagulants / metabolism*
  • Aryl Hydrocarbon Hydroxylases / chemistry
  • Aryl Hydrocarbon Hydroxylases / genetics
  • Aryl Hydrocarbon Hydroxylases / metabolism*
  • Cytochrome P-450 CYP2C9
  • Dose-Response Relationship, Drug
  • European Continental Ancestry Group / genetics*
  • Female
  • Genotype
  • Humans
  • Hydroxylation
  • In Vitro Techniques
  • Japan
  • Linkage Disequilibrium
  • Male
  • Metabolic Clearance Rate
  • Middle Aged
  • Mutagenesis, Site-Directed
  • NADPH-Ferrihemoprotein Reductase / metabolism*
  • Polymerase Chain Reaction
  • Polymorphism, Genetic*
  • Temperature
  • Warfarin / metabolism*

Substances

  • Anticoagulants
  • Warfarin
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases
  • NADPH-Ferrihemoprotein Reductase