The term CYTOCHROME P-450 refers to a group of enzymes with are located on the endoplasmic reticulum. These enzymes are of particular importance when studying drug biotransformation and drug metabolism.
It is know that the gene for cytochrome P-450 has existed for more then 3.5 billion years. This indicates drug metabolism by the P-450 system is a new and secondary role for these enzyme systems.
The primary role for the P450 system seems to be one of metabolism and detoxification of endogenous compounds after they have been taken in by mouth in the process of eating. This accounts for the high concentrations of these enzymes located in the liver and small intestine.
The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids, and other lipids.
THE CYTOCHROME P-450 ENZYME SYSTEM
Pharmacokinetics: Substrates, Inhibitors and Inducers of CYP 450
Drug metabolism - cytochrome P450 - Homo sapiens