CYP2C9 gene

cytochrome P450 family 2 subfamily C member 9

The CYP2C9 gene provides instructions for making an enzyme that is found in a cell structure called the endoplasmic reticulum, which is involved in protein processing and transport. The CYP2C9 enzyme breaks down (metabolizes) compounds including steroid hormones and fatty acids. The CYP2C9 enzyme also plays a major role in breaking down the drug warfarin, which thins the blood and prevents blood clots from forming. This enzyme also assists in metabolizing other drugs such as ibuprofen, which reduces inflammation.

Certain common CYP2C9 gene variations (polymorphisms) that decrease the activity of the CYP2C9 enzyme can result in a condition called warfarin sensitivity. The altered enzyme slows the breakdown (metabolism) of warfarin, allowing the drug to remain active in the body for a longer period of time. People with warfarin sensitivity take longer than usual to metabolize warfarin and may require lower doses of the drug than are usually prescribed.

The two most common CYP2C9 gene polymorphisms change single protein building blocks (amino acids) in the CYP2C9 enzyme. The first one, known as CYP2C9*2, replaces the amino acid arginine with the amino acid cysteine at position 144, written as Arg144Cys or R144C. The CYP2C9*2 polymorphism leads to a decrease in warfarin metabolism to such a degree that prescription doses are typically reduced by one-third in people with this variation. The second polymorphism, known as CYP2C9*3, replaces the amino acid isoleucine with the amino acid leucine at position 359, written as Ile359Leu or I359L. In people with the CYP2C9*3 polymorphism, prescription doses are typically reduced by one-fifth. In rare cases in which individuals have both CYP2C9*2 and CYP2C9*3 polymorphisms, the enzyme activity is severely decreased and metabolism of warfarin is very slow. If people with warfarin sensitivity take the average dose (or more) of warfarin, they are at risk of an overdose, which can cause abnormal bleeding in the brain, gastrointestinal tract, or other tissues, and may lead to serious health problems or death.

Cytogenetic Location: 10q23.33, which is the long (q) arm of chromosome 10 at position 23.33

Molecular Location: base pairs 94,938,658 to 94,989,391 on chromosome 10 (Homo sapiens Annotation Release 109, GRCh38.p12) (NCBI)

Cytogenetic Location: 10q23.33, which is the long (q) arm of chromosome 10 at position 23.33
  • cytochrome P-450MP
  • cytochrome P450 2C9
  • cytochrome P450 MP-4
  • cytochrome P450 MP-8
  • cytochrome P450 PB-1
  • cytochrome P450, family 2, subfamily C, polypeptide 9
  • cytochrome P450, family 2, subfamily C, polypeptide 9 gene
  • P450 MP-4
  • S-mephenytoin 4-hydroxylase
  • S-mephenytoin 4-hydroxylase, human
  • warfarin-7-hydroxylase, human