Regular ArticleThe Effects of Cytochrome b5, NADPH-P450 Reductase, and Lipid on the Rate of 6β-Hydroxylation of Testosterone as Catalyzed by a Human P450 3A4 Fusion Protein
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Distinct effects of form selective cytochrome P450 inhibitors on cytochrome P450-mediated monooxygenase and hydrogen peroxide generating NADPH oxidase
2022, Toxicology and Applied PharmacologyCitation Excerpt :In contrast, in both rat recombinant CYP3A1 and CYP3A2, and rat microsomes enriched with CYP3A subfamily enzymes, ketoconazole, which inhibited their monooxygenase activities, only partially inhibited their H2O2 generating activity. These latter findings are consistent with earlier work using a human recombinant CYP3A4 (Shet et al., 1995). In these studies ketoconazole (0.5–1 μM) completely blocked monooxygenase activity, as measured by 6β hydroxylation of testosterone, but only partially blocked NADPH oxidase activity as measured by H2O2 generation.
Role of cytochrome b5 in the modulation of the enzymatic activities of cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1)
2017, Journal of Steroid Biochemistry and Molecular BiologyCooperativity in cytochrome P450 3A4: Linkages in substrate binding, spin state, uncoupling, and product formation
2007, Journal of Biological ChemistryCitation Excerpt :Comparison of the titration curves shown in Fig. 4 reveals an almost identical high-spin shift caused by TS binding by CYP3A4 in the presence or absence of CPR. The steady-state NADPH oxidation rates measured over a broad range of TS concentrations are faster than those previously measured for CYP3A4 (3, 5, 47). The nature of this acceleration of NADPH consumption in CYP3A4·CPR Nanodiscs may be attributed to the close proximity of CPR to cytochrome P450 when both proteins are confined in a 12-nm Nanodisc with an effective phospholipid bilayer diameter of ∼9.0 nm.