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Tyrosine nitration by simultaneous generation of (NO)-N-center dot and O-2(center dot) under physiological conditions - How the radicals do the job
KTH, Superseded Departments, Chemistry.
KTH, Superseded Departments, Chemistry.
2000 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 275, no 5, 3031-3036 p.Article in journal (Refereed) Published
Abstract [en]

Radiation chemical experiments demonstrate that the reaction of tyrosyl radical (TyrO(.)) with (NO2)-N-. yields 45 +/- 3% 3-nitrotyrosine and that a major product of the reaction of TyrO(.) with (NO)-N-. is 3,3'-dityrosine. Radiolysis was used to generate (NO)-N-. and O-2(-.) in the presence of tyrosine and bicarbonate at pH 7.5 +/- 0.1. The nitration yield was found to be dose rate-dependent, and the yield per radical produced by pulse radiolysis was identical to that obtained with authentic peroxynitrite, The proposed mechanism that accounts for the data is as follows: (i) In the presence of CO2 the reaction of (NO)-N-. with O-2(-.) yields 33% (NO2)-N-. and CO3-. where the latter reacts rapidly with tyrosine to form TyrO; (ii) The formation of 3-nitrotyrosine takes place via the reaction of (NO2)-N-. with TyrO(.), which is the main process at high dose rates; and (iii) Under continuous generation of (NO)-N-. and O-2(-.) the formation of 3-nitrotyrosine is strongly suppressed because of efficient scavenging of NO2, by tyrosine. The proposed model shows that the highest nitration yield is obtained for similar fluxes of (NO)-N-. and O-2(-.) and is completely inhibited upon excess production of O-2(-.) because of efficient scavenging of TyrO(.) by O-2(-.). The biological implications of these findings are discussed.

Place, publisher, year, edition, pages
2000. Vol. 275, no 5, 3031-3036 p.
Keyword [en]
nitric-oxide solutions, carbon-dioxide, biological-activity, hydrogen-peroxide, phenoxyl radicals, aqueous-solutions, oxidative damage, peroxynitrite, mechanism, no
URN: urn:nbn:se:kth:diva-19515ISI: 000085146500004OAI: diva2:338207
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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