CYP2C9 encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are phase I detoxification enzymes which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. CYP2C9 expression is induced by rifampin. The enzyme is known to metabolize many xenobiotics, including phenytoin, tolbutamide, ibuprofen and S-warfarin. Studies identifying individuals who are poor metabolizers of phenytoin and tolbutamide suggest that this gene is quite variable among individuals. CYP2C9 is an important cytochrome P450 enzyme with a major role in the oxidation of both xenobiotic and endogenous compounds. CYP2C9 makes up about 18% of the cytochrome P450 protein in the liver. Some 100 therapeutic drugs are metabolized ㅡby CYP2C9, including drugs with a narrow therapeutic index such as warfarin and phenytoin and other routinely prescribed drugs such as acenocoumarol, tolbutamide, losartan, glipizide, and some nonsteroidal anti-inflammatory drugs. The CYP2C9 gene is highly polymorphic. More than 50 single nucleotide polymorphisms (SNPs) have been described.
CYP family in general may play a much larger role in redox mechanisms as it is a major consumer of NADPH, an important reducing agent for glutathione recycling. These enzymes also play a major role in cell danger signaling and cell turnover as it interacts electrically with the apoptosis mechanisms controlled by mitochondria.