The kinetics of oxidation of GSH by protein radicals

Thomas Nauser, Willem H. Koppenol, Janusz M. Gebicki*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    68 Citations (Scopus)

    Abstract

    Current studies provide evidence that proteins are initial targets of ROS (reactive oxygen species) in biological systems and that the damaged proteins can in turn damage other cell constituents. This study was designed to test the possibility that protein radicals generated by ROS can oxidize GSH and assess the probability of this reaction in vivo by measurement of the rate constant of this reaction. Lysozyme radicals were generated by hydroxyl and azide radicals in steady-state gamma ray radiolysis. In the absence of dioxygen, a range of protein carbon-centred amino acid radicals were produced by the hydroxyl radicals, and defined tryptophan radicals by the azide radicals. In the presence of dioxygen, each carbon-centred radical was converted to a protein peroxyl radical. Each of the peroxyl radicals was able to oxidize a molecule of GSH, regardless of its location in the protein. The peroxyl radicals were 10 and 20 times more effective GSH oxidants than the carbon-centred radicals produced randomly in the lysozyme, or the defined tryptophan lysozyme radicals respectively. We obtained for the first time the rate constant of reaction between a protein free-radical and GSH. Lysozyme tryptophan carbon radicals generated by nanosecond pulse radiolysis and flash photolysis oxidized GSH with a rate constant of (1.05 ± 0.05) × 105 M-1 · s-1. Overall, the results are consistent with the hypothesis that protein radicals may be important intermediates in the pathway linking oxidative stress and damage in living organisms and emphasize the strongly enhancing role of dioxygen in this process.

    Original languageEnglish
    Pages (from-to)693-701
    Number of pages9
    JournalBiochemical Journal
    Volume392
    Issue number3
    DOIs
    Publication statusPublished - 15 Dec 2005

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