Human cytochrome P450 enzymes

Abstract

The cytochrome P450 (P450) enzymes first attracted interest because of their relevance to the metabolism of drugs, steroids, and carcinogens. Collectively, the 57 human P450s are involved in approximately three fourths of the metabolism of marketed drugs. Many of the steroid-oxidizing P450s have important roles in endocrinology. The roles of individual P450s can be predicted during drug development, and many drug–drug interactions are understood in the context of P450s. The human P450s involved in the metabolism of many carcinogens have been identified, and this information forms the basis for investigation into the human risk of these chemicals. Many questions still remain about the physiological roles of many human P450s, the relevance of the reactions they catalyze, and even the chemistry of some of the reactions. In this chapter, each of the 57 human P450s is discussed regarding current information about sites of expression, regulation, genetic variation, substrates and reactions, structures, inhibitors, and clinical issues.