Pressure modulation of cytochrome-to-cytochrome electron-transfer. Models and enzyme reactions.
The kinetics of electron-transfer involved in reactions of reduction of 2,6-dichlorophenol indophenol and Fe(CN)3-(6) by L-ascorbic acid and reduction of ferric cytochrome c by both L-ascorbic acid and reduced hydroxylamine oxidoreductase were studied as a function of three parameters: ionic strength, pressure (1-2000 bar) and temperature (4-20 degrees C) using the high-pressure stopped-flow method. From measurements, the thermodynamic parameters of activation volume (delta V++), and, when possible, activation enthalpy and entropy (delta H++ and delta S++) have been calculated. We found, for these four systems, that the pressure has revealed solvation effects involved in electron-transfer. For the reduction of ferric cytochrome c by reduced hydroxylamine oxidoreductase (a cytochrome-to-cytochrome electron-transfer), we have not obtained evidence for a conformational change.
Heiber-Langer
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I
Institut National de la Santé et de la Recherche Médicale, U 128, CNRS, Montpellier, France.
Hooper
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Balny
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C
D015086:2,6-Dichloroindophenol / Q000737:chemistry; D000465:Algorithms; D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D003574:Cytochrome c Group / Q000032:analysis* / Q000737:chemistry; D004579:Electron Transport; D006736:Horses; D006874:Hydrostatic Pressure; D007700:Kinetics; D008954:Models, Biological; D010088:Oxidoreductases / Q000032:analysis; D013816:Thermodynamics
D003574:Cytochrome c Group; D015086:2,6-Dichloroindophenol; D010088:Oxidoreductases; C021401:hydroxylamine dehydrogenase; D001205:Ascorbic Acid