Catalytic selectivity of human cytochrome P450 enzymes: relevance to drug metabolism and toxicity.

About 30 different human cytochrome P450 (P450) enzymes have now been characterized in considerable detail. It is possible to elucidate their catalytic specificities towards drugs, steroids, carcinogens, and other potential substrates with in vitro assays. It is also possible to ascertain the levels of individual P450 enzymes in humans with the use of drugs, after appropriate assay validation. The ability to discern catalytic selectivity and levels of P450 enzymes within individuals offers considerable potential in drug development, prevention of undesirable drug-drug interactions, and understanding the etiology of diseases resulting from exposure to potentially toxic and carcinogenic chemicals.