Role of cytochrome b5 in the cytochrome P-450-mediated C21-steroid 17,20-lyase reaction |
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| Authors: | Masayuki Katagiri Katsuko Suhara Masahiro Shiroo Yoshiyuki Fujimura |
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| Affiliation: | Department of Chemistry, Faculty of Science Kanazawa University, Kanazawa 920, Japan |
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| Abstract: | The cytochrome P-450 (P-450sccII) and its reductase, NADPH-cytochrome reductase [EC 1.6.2.4], associated with conversion of progesterone to 4-androstene-3,17-dione, were extensively purified from pig testis microsomes. Higher lyase activity (turnover number of 15 mol of the product formed/min/mol of P-450) could be restored by mixing the P-450sccII, its reductase, pig liver cytochrome b5 and cytochrome b5-reductase [EC 1.6.2.2], and phospholipid in the presence of NADPH, NADH, and O2. Omission of either cytochrome b5 or NADH resulted in a significant loss of the lyase activity indicating actual participation of cytochrome b5 in this P-450-mediated steroidogenic system in the testis. |
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| Keywords: | androstenedione 4-androstene-3,17-dione FpD FpT NADPH-cytochrome reductase [EC 1.6.2.4] P-450 cytochrome P-450 SDS sodium dodecyl sulfate |
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