Mechanism of ascorbic acid oxidation by cytochrome b(561)
| Autor: | Wigle M, Schlegel Hb, Kipp Bh, Patrick M. Kelley, David Njus |
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| Rok vydání: | 2001 |
| Předmět: |
Models
Molecular Cytochrome Electron donor Ascorbic Acid Photochemistry Biochemistry Medicinal chemistry Redox chemistry.chemical_compound Electron transfer Animals Histidine Cytochrome b561 biology Cytochrome b Active site Hydrogen Bonding Hydrogen-Ion Concentration Ascorbic acid Cytochrome b Group Kinetics chemistry biology.protein Thermodynamics Cattle Oxidation-Reduction |
| Zdroj: | Biochemistry. 40(39) |
| ISSN: | 0006-2960 |
| Popis: | The 1 equiv reaction between ascorbic acid and cytochrome b(561) is a good model for redox reactions between metalloproteins (electron carriers) and specific organic substrates (hydrogen-atom carriers). Diethyl pyrocarbonate inhibits the reaction of cytochrome b(561) with ascorbate by modifying a histidine residue in the ascorbate-binding site. Ferri/ferrocyanide can mediate reduction of DEPC-treated cytochrome b(561) by ascorbic acid, indicating that DEPC-inhibited cytochrome b(561) cannot accept electrons from a hydrogen-atom donor like ascorbate but can still accept electrons from an electron donor like ferrocyanide. Ascorbic acid reduces cytochrome b(561) with a K(m) of 1.0 +/- 0.2 mM and a V(max) of 4.1 +/- 0.8 s(-1) at pH 7.0. V(max)/K(m) decreases at low pH but is approximately constant at pH >7. The rate constant for oxidation of cytochrome b(561) by semidehydroascorbate decreases at high pH but is approximately constant at pH |
| Databáze: | OpenAIRE |
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