Abstract
We have employed a novel photoreduction system to investigate the electron-transfer reaction between cytochrome c and cytochrome c oxidase.In this system,the photogenerated uroporphyrin triplet state is quenched through electrontransfer to ferricytochrome c.The corresponding uroporphyrin«--cationradicalis rapidly reduced by nicotinamideadeninedinudeotide(NADH) resulting in the insitugeneration of ferrocytochrome c.In the presence of cytochromec oxidase,cytochromec is reoxidized biphasically while the corresponding reduction of cytochrome a appears to be monophasic.In addition,the fast-phase rate constants are dependent upon the concentration of cytochromec oxidase giving a first-order in tracomplexelectron-transferrate constant,(£«),of1829±248s"1.The ratio of electrons transferred from ferrocytochrome c to cytochromeais1:1indicating that cytochromea is the ultimate acceptor of the electrons.