Requirements for superoxide-dependent tyrosine hydroperoxide formation in peptides

Christine C. Winterbourn*, Helena N. Parsons-Mair, Silvia Gebicki, Janusz M. Gebicki, Michael J. Davies

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    91 Citations (Scopus)


    Superoxide reacts rapidly with other radicals, but these reactions have received little attention in the context of oxidative stress. For tyrosyl radicals, reaction with superoxide is 3-fold faster than dimerization, and forms the addition product tyrosine hydroperoxide. We have explored structural requirements for hydroperoxide formation using tyrosine analogues and di- and tri-peptides. Superoxide and phenoxyl radicals were generated using xanthine oxidase, peroxidase and the respective tyrosine derivative, or by γ-radiation. Peroxides were measured using FeSO4/ Xylenol Orange. Tyrosine and tyramine formed stable hydroperoxides, but N-acetyltyrosine and p-hydroxyphenylacetic acid did not, demonstrating a requirement for a free amino group. Using [14C]tyrosine, the hydroperoxide and dityrosine were formed at a molar ratio of 1.8:1. Studies with pre-formed hydroperoxides, and measurements of substrate losses, indicated that, in the absence of a free amino group, reaction with superoxide resulted primarily in restitution of the parent compound. With dipeptides, hydroperoxides were formed only on N-terminal tyrosines. However, adjacent lysines promoted hydroperoxide formation, as did addition of free lysine or ethanolamine. Results are compatible with a mechanism [d'Alessandro, Bianchi, Fang, Jin, Schuchmann and von Sonntag (2000) J. Chem. Soc. Perkin Trans. II, 1862-1867] in which the phenoxyl radicals react initially with superoxide by addition, and the intermediate formed either releases oxygen to regenerate the parent compound or is converted into a hydroperoxide. Amino groups favour hydroperoxide formation through Michael addition to the tyrosyl ring. These studies indicate that tyrosyl hydroperoxides should be formed in proteins where there is a basic molecular environment. The contribution of these radical reactions to oxidative stress warrants further investigation.

    Original languageEnglish
    Pages (from-to)241-248
    Number of pages8
    JournalBiochemical Journal
    Issue number1
    Publication statusPublished - 1 Jul 2004


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