title: Human cytochromes P450: problems and prospects.
abstract: Cytochromes P450 are a superfamily of haem-containing monooxygenases. In mammals, two general classes of P450s exist: six families involved in steroid and bile acid biosynthetic pathways of metabolism; four families containing numerous individual P450s, mainly responsible for metabolism of foreign compounds. Many of the latter P450s, particularly those in the CYP2 family, exhibit a large degree of inter- and intra-species variability in regulation and catalytic activities. From a practical standpoint, these variabilities suggest the need for careful characterization of P450 catalytic activities and determination of P450 expression levels in humans. Human P450-based in vitro systems are being developed to evaluate drug and carcinogen metabolism.
authors.affiliation: National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: F J
authors.initials: FJ
authors.lastname: Gonzalez
mesh_terms: D001647:Bile Acids and Salts / Q000378:metabolism; D001711:Biotransformation; D002273:Carcinogens / Q000493:pharmacokinetics*; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D013256:Steroids / Q000378:metabolism; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D001647:Bile Acids and Salts; D002273:Carcinogens; D013256:Steroids; D015262:Xenobiotics; D003577:Cytochrome P-450 Enzyme System