Kinetic studies on redox reactions of hemoproteins. II. Reduction of thermoresistant cytochrome c-552 and horse heart cytochrome c by ascorbic acid.
The reductions of thermoresistant cytochrome c-552 and horse heart cytochrome c by ascorbic acid were studied by the stopped-flow method between pH 4 and 10. The results were as follows (1) The reduction of horse heart cytochrome c showed two relaxation decays above pH 8.5, one of which was pseudo-first order, as was the case below pH 8, while the other was nearly concentration-independent. These results were consistent with those reported by Greenwood and Palmer (J. Biol. Chem. (1965) 240, 3660-3663). (2) For the reduction of cytochrome c-552, only a single relaxational decay that obeyed pseudo-first order kinetics was observed. (3) It seems most reasonable to assume that the concentration-independent relaxation process can be attributed to the isomerization reaction accompanying ligand exchange, since it is known that only horse heart cytochrome c exhibits ligand exchange, involving a residue with pK 9.3.
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000378:metabolism*; D005292:Ferricyanides / Q000378:metabolism; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009206:Myocardium; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D013696:Temperature
D003574:Cytochrome c Group; D005292:Ferricyanides; D001205:Ascorbic Acid