Oxidative stress, reactive species and antioxidants Repair of protein radicals

J. Gebicki, Anastasia S. Domazou, Thomas Nauser, Daniel Steinmann, Willem H. Koppenol

    Research output: Contribution to journalMeeting abstractpeer-review


    Hydroxyl radicals and peroxynitrous acid oxidize proteins, which
    ultimately results in their denaturation. Random radical generation on
    the surface of the protein without dioxygen present leads to intramolecular
    electron transfer, with the last step the oxidation of tyrosine
    by the tryptophanyl radical. In the presence of dioxygen aliphatic
    radicals form oxidizing peroxyl radicals. Once a radical is formed,
    can it be repaired, does it react with dioxygen or is it ‘‘repaired’’ by
    intramolecular electron transfer?
    Glutathione repairs a tryptophan radical in lysozyme with a rate
    constant of (1.05 ± 0.05) × 105 M-1s-1, while ascorbate repairs
    tryptophanyl and tyrosyl radicals ca. three orders of magnitude faster.
    Glutathione generally reacts slowly, such that formation of peroxyl
    radicals cannot be prevented. These peroxyl radicals are reduced by
    glutathione to hydroperoxides, a process that cannot be characterized
    as a repair. Furthermore, the resulting thiyl radical is capable of
    hydrogen abstraction. Although physiologically not significant, selenoglutathione
    reduces tyrosyl radicals as fast as ascorbate. The
    reaction of protein radicals (insulin, b-lactoglobulin, pepsin, chymotrypsin,
    and bovine serum albumin) with ascorbate is competitive
    with dioxygen, leaves an innocuous ascorbyl radical, and is therefore
    a true repair. The well-documented loss of ascorbate in living
    organisms subjected to oxidative stress may result from repair of
    protein radicals.
    Original languageEnglish
    Pages (from-to)S35-S36
    Number of pages2
    JournalAmino Acids
    Issue number1
    Publication statusPublished - Jul 2009


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