| On the function of cytochrome b5 in the cytochrome P-450-dependent oxygenase system. | |
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MedLine Citation:
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PMID: 6696448 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Complex formation between the phenobarbital-inducible form of rabbit liver microsomal cytochrome P-450 incorporated into phosphatidylcholine and detergent-solubilized cytochrome b5 is associated with a low-to-high spin transition of the former pigment. It is concluded that the proteins combine in a 1:1 molar ratio. CD spectral analysis in the far uv region reveals that interaction of the cytochromes results in a conformational change of one or both hemoproteins. Such a cytochrome b5-induced structural alteration of the reconstituted enzyme system is accompanied by an increase in affinity of 4-chloroaniline for cytochrome P-450, as measured in terms of cumene hydroperoxide-supported N-oxidation of the arylamine; the maximum velocity of the catalytic process remains unchanged. Similarly, incorporation into the assay media of cytochrome b5 decreases the apparent Kd values of both the amine substrate and the oxygen donor, as determined by optical titration. Stopped-flow spectrophotometric studies on the influence of cytochrome b5 on the kinetics of binding to cytochrome P-450 of 4-chloroaniline and/or cumene hydroperoxide show that the rates of formation and decay of the adducts change as the molar ratio of cytochrome b5 to cytochrome P-450 varies. Moreover, cytochrome b5 modifies the activation energies required for production of the substrate-bound oxy complex. These findings suggest that cytochrome b5, apart from its well-known role as an electron carrier, might exert an effector function in the cytochrome P-450 system. |
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Authors:
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P Hlavica |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Archives of biochemistry and biophysics Volume: 228 ISSN: 0003-9861 ISO Abbreviation: Arch. Biochem. Biophys. Publication Date: 1984 Feb |
Date Detail:
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Created Date: 1984-03-12 Completed Date: 1984-03-12 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0372430 Medline TA: Arch Biochem Biophys Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 600-8 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Aniline Compounds
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metabolism Animals Benzene Derivatives / metabolism Catalysis Cytochrome P-450 Enzyme System Cytochrome b Group / physiology* Cytochromes b5 Energy Transfer Female Male Microsomes, Liver / enzymology* Oxygenases / metabolism* Phospholipids / metabolism Rabbits Temperature |
| Chemical | |
Reg. No./Substance:
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0/Aniline Compounds; 0/Benzene Derivatives; 0/Cytochrome b Group; 0/Phospholipids; 106-47-8/4-chloroaniline; 80-15-9/cumene hydroperoxide; 9035-39-6/Cytochromes b5; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.13.-/Oxygenases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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