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.
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Research Article|
June 22 2004
Requirements for superoxide-dependent tyrosine hydroperoxide formation in peptides
Christine C. WINTERBOURN;
Christine C. WINTERBOURN
1
*Department of Pathology, Christchurch School of Medicine and Health Sciences, P.O. Box 4345, Christchurch, New Zealand
1To whom correspondence should be addressed (e-mail christine.winterbourn@chmeds.ac.nz).
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Helena N. PARSONS-MAIR;
Helena N. PARSONS-MAIR
*Department of Pathology, Christchurch School of Medicine and Health Sciences, P.O. Box 4345, Christchurch, New Zealand
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Silvia GEBICKI;
Silvia GEBICKI
†Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
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Janusz M. GEBICKI;
Janusz M. GEBICKI
†Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
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Michael J. DAVIES
Michael J. DAVIES
‡The Heart Research Institute, 145–147 Missenden Road, Camperdown, Sydney, NSW 2050, Australia
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Publisher: Portland Press Ltd
Received:
February 17 2004
Revision Received:
March 12 2004
Accepted:
March 16 2004
Accepted Manuscript online:
March 16 2004
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2004
Biochem J (2004) 381 (1): 241–248.
Article history
Received:
February 17 2004
Revision Received:
March 12 2004
Accepted:
March 16 2004
Accepted Manuscript online:
March 16 2004
Citation
Christine C. WINTERBOURN, Helena N. PARSONS-MAIR, Silvia GEBICKI, Janusz M. GEBICKI, Michael J. DAVIES; Requirements for superoxide-dependent tyrosine hydroperoxide formation in peptides. Biochem J 1 July 2004; 381 (1): 241–248. doi: https://doi.org/10.1042/BJ20040259
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