Efficient repair of protein radicals by ascorbate
Efficient repair of protein radicals by ascorbate
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DOI：
10.1016/j.freeradbiomed.2009.01.001
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发表时间：
2009-04-15
影响因子：
7.4
通讯作者：
Gebicki, Janusz M.
中科院分区：
文献类型：
--
作者：
Domazou, Anastasia S.;Koppenol, Willem H.;Gebicki, Janusz M.
胰岛素、β -乳球蛋白、胃蛋白酶、凝乳胰蛋白酶和牛血清白蛋白中Trp和Tyr残基上的叠氮自由基选择性地产生蛋白质自由基，速率常数在（2.9-19）× 10(8) M-1 s（-1）范围内。单氢抗坏血酸降低凝乳胰蛋白酶和胃蛋白酶中的色氨酸自由基的速率常数在（1.6-1.8）× 10(8) M-1 s（-1）的狭窄范围内，而β -乳球蛋白色氨酸自由基的反应速度几乎慢了10倍。蛋白质酪氨酸自由基的相应值大约要小一个数量级。比较游离和蛋白结合的色氨酸和酪氨酸自由基的反应速率常数表明，在大多数情况下，自由基在蛋白链上的位置并不构成与抗坏血酸单氢反应的主要障碍。结果表明，在双氧的生理浓度下，单氢抗坏血酸可能是蛋白质自由基的重要目标。因此，与蛋白质自由基的反应可能是氧化应激下生物体内抗坏血酸损失的主要原因。(C) 2009爱思唯尔公司版权所有。
Protein radicals were selectively generated by reaction with azide radicals on Trp and Tyr residues in insulin, beta-lactoglobulin, pepsin, chymotrypsin, and bovine serum albumin at rate constants in the range (2.9-19) x 10(8) M-1 s(-1). Monohydrogen ascorbate reduced tryptophanyl radicals in chymotrypsin and pepsin with rate constants in the narrow range of (1.6-1.8) x 10(8) M-1 s(-1), whereas beta-lactoglobulin tryptophanyl radicals reacted almost 10 times slower. The corresponding values for the protein tyrosyl radicals were about an order of magnitude smaller. Comparison of the rate constants of reactions of free and protein-bound tryptophanyl and tyrosyl radicals showed that, in most cases, the location of the radicals in the protein chain did not constitute a major barrier to the reaction with monohydrogen ascorbate. The results suggest that, under physiological concentrations of dioxygen, monohydrogen ascorbate is likely to be a significant target of protein radicals. It seems likely, therefore, that reaction with protein radicals may be responsible for much of the well-documented loss of ascorbate in living organisms subjected to oxidative stress. (C) 2009 Elsevier Inc. All rights reserved.