Monooxygenase catalysts play key roles in activation and detoxication of organic xenobiotics including carcinogens, drugs, and pollutants. Cytochrome P-450 is dominant in oxidative metabolism and activation of foreign compounds, and isozymes of cytochrome P-450 could determine the effects of chemicals in different organs, individuals or species. The overall objective of this research is to establish the nature of biotransformation enzymes, especially cytochrome P-450 isozymes, in non- mammalian and aquatic species. Currently it is difficult to critically compare cytochrome P-450 isozymes of non-mammalian species with each other, because definitive knowledge of these isozymes in these species is scant. Basic aspects concerning cytochrome P-450 isozymes and their regulation must be known in order to understand the similarities and differences of their functions among different species, and to evaluate and compare species responses to xenobiotics. Multiple forms of cytochrome P-450 will be purified from liver of the marine fish Stenotomus chrysops (scup). Efforts will be directed toward cytochromes P- 450A to P-450E, which compose the majority of scup liver microsomal P-450. Isozymes will be characterized for catalytic and physico-chemical properties. NADPH-cytochrome P-450 reductase and cytochrome bs will also be purified. Polyclonal antibodies to cytochrome P-450 forms A-E and cytochrome b5, and monoclonal antibodies to cytochrome P-450A, will be prepared. Antibodies will be used in immunoblotting and ELISA to study regulation of cytochrome P-450 forms in fish liver by selected inducers, assessing the turnover of cytochrome P-450, and the regulation of major forms of cytochrome P-450 in extrahepatic organs of scup. Antibodies will also be used to evaluate the contribution of different isozymes to xenobiotic and steroid metabolism in non-mammalian microsomal systems, and to evaluate the similarities of cytochromes P-450 in selected non- mammalian and mammalian species. In addition to the above aims, we will determine the feasibility of using molluscan species to study flavoprotein monooxygenase function, evaluating the hypothesis that his enzyme is involved in activating carcinogenic amines in these invertebrates. Results could provide information and probes for evaluating various non-mammalian species or even cell lines for mechanisms of xenobiotic metabolism.
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