ABSTRACT The strong power of cytochrome c to scavenge O2-. and H2O2 can be observed by the comparison of H2O2 generation in the preparations of cytochrome c depleted respiratory chain and the chain containing cytochrome c with the electron transfer blocked by antimycin. It is observed that the H2O2 generation in the cytochrome c depleted preparation is about 20 times more than that in antimycin blocked preparation. Such big dispersion is because that the H2O2 is accumulated in the cytochrome c depleted preparation whereas in the antimycin blocked preparation the H2O2 is scavenged by cytochrome c through the cytochrome c-mediated electron leak pathways of respiratory chain. In order to explain the strong power of cytochrome c to scavenge H2O2, the chemical property of the reaction of ferrocytochrome c and H2O2 is investigated. The most surprising finding is that the reaction of ferrocytochrome c and H2O2 is not in the stoichiometric relationship of redox reaction but in an enzyme-like reaction. It is shown that about 25,000 molecules of H2O2 can be reduced per one molecule oxidation of ferrocytochrome c. The biological significance of cytochrome c having such strong power to scavenge O2-. and H2O2 is discussed in the context of evolution of respiratory chain.
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