Towards Understanding Cytochromes P450

For more than four decades cytochrome P450 (CYP) has been the subject of intense investigation, largely as a result of its catalytic diversity. Not only is CYP responsible for the metabolism of tens of thousands of xenobiotics (e.g. drugs, industrial chemicals, environmental pollutants, plant products and toxins), but the enzyme is essential also for the biosynthesis and catabolism of a broad range of endogenous compounds, including bile acids, biogenic amines, eicosanoids, fatty acids and steroid hormones. Of greatest relevance to this review article.however, is the role of CYP in xenobiotic metabolism. Humans are exposed to an array of xenobiotics capable of exerting a broad range of pharmacological and toxicological effects. In most instances CYP-mediated biotransformation serves as a detoxification mechanism since the metabolites formed generally possess less biological activity than the parent compound. CYP-mediated biotransformation additionally facilitates the elimination of typically lipophilic xenobiotics and the newly introduced functional group may serve as an acceptor for conjugating enzymes (e.g. UDP-glucuronosyltransferase, sulphotransferase, glutathione transferase), enhancing renal clearance further.