Cytochrome P450 2C9 (CYP2C9, EC 1.14.14.1) is a member of the cytochrome P450 monooxidase (CYP) family of microsomal xenobiotic metabolism enzymes. CYPs are membrane-bound hemeproteins responsible for Phase I biotransformation reactions, in which lipophilic drugs and other xenobiotic compounds are converted to more hydrophilic products to facilitate excretion from the body. In the liver, this enzyme contributes to the wide pharmacokinetic variability of the metabolism of drugs such as S-warfarin, diclofenac, phenytoin, tolbutamide and losartan.

CYP2C9 gene is highly polymorphic. More than 50 single nucleotide polymorphisms (SNPs) have been described in the regulatory and coding regions of the CYP2C9 gene, some of which are associated with reduced enzyme activity compared with wild type in vitro. Extrahepatic CYP2C9 often metabolizes endogenous compounds such as arachidonic acid, 5-hydroxytryptamine, and linoleic acid. BioVision’s EZCypTM 2C9 is a permeabilized and stabilized dried yeast powder preparation containing recombinant human CYP2C9 and recombinant human P450 NADPH oxidoreductase co expressed in the same preparation.