Nauser Thomas, Gebicki Janusz M
Laboratorium für Anorganische Chemie, Departement für Chemie und Angewandte Biowissenschaften, Eidgenössische Technische Hochschule (ETH) Zürich, CH - 8093 Zürich, Switzerland.
Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Arch Biochem Biophys. 2017 Nov 1;633:118-123. doi: 10.1016/j.abb.2017.09.011. Epub 2017 Sep 20.
Reaction kinetics of amino acid and peptide alkyl radicals with GSH and ascorbate, the two most abundant endogenous antioxidants, were investigated by pulse radiolysis. Rate constants in the order of 10 Ms were found. Alkyl radicals react at almost diffusion controlled rates and irreversibly with oxygen to form peroxyl radicals, and competition with this reaction is the benchmark for efficient repair in vivo. We consider repair of protein radicals and assume comparable rate constants for the reactions of GSH/ascorbate with peptide alkyl radicals and with alkyl radicals on a protein surface. Given physiological concentrations of oxygen, GSH and ascorbate, protein peroxyl radicals will always be a major product of protein alkyl radicals in vivo. Therefore, if they are formed by oxidative stress, protein alkyl radicals are a probable cause for biological damage.
通过脉冲辐解研究了氨基酸和肽烷基自由基与两种最丰富的内源性抗氧化剂谷胱甘肽（GSH）和抗坏血酸的反应动力学。发现速率常数约为10⁹ M⁻¹s⁻¹。烷基自由基以几乎扩散控制的速率与氧气发生不可逆反应形成过氧自由基，与该反应的竞争是体内有效修复的基准。我们考虑蛋白质自由基的修复，并假设GSH/抗坏血酸与肽烷基自由基以及与蛋白质表面烷基自由基反应的速率常数相当。考虑到体内氧气、GSH和抗坏血酸的生理浓度，蛋白质过氧自由基将始终是体内蛋白质烷基自由基的主要产物。因此，如果蛋白质烷基自由基是由氧化应激形成的，那么它们很可能是生物损伤的原因。
