Center for Advanced Technology, and Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznanskiego 10, 61-712 Poznan, Poland.
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland.
Molecules. 2022 Feb 2;27(3):1028. doi: 10.3390/molecules27031028.
Oxidation of methionine (Met) is an important reaction that plays a key role in protein modifications during oxidative stress and aging. The first steps of Met oxidation involve the creation of very reactive and short-lived transients. Application of complementary time-resolved radiation and photochemical techniques (pulse radiolysis and laser flash photolysis together with time-resolved CIDNP and ESR techniques) allowed comparing in detail the one-electron oxidation mechanisms initiated either by OH radicals and other one-electron oxidants or the excited triplet state of the sensitizers e.g., 4-,3-carboxybenzophenones. The main purpose of this review is to present various factors that influence the character of the forming intermediates. They are divided into two parts: those inextricably related to the structures of molecules containing Met and those related to external factors. The former include (i) the protection of terminal amine and carboxyl groups, (ii) the location of Met in the peptide molecule, (iii) the character of neighboring amino acid other than Met, (iv) the character of the peptide chain (open vs cyclic), (v) the number of Met residues in peptide and protein, and (vi) the optical isomerism of Met residues. External factors include the type of the oxidant, pH, and concentration of Met-containing compounds in the reaction environment. Particular attention is given to the neighboring group participation, which is an essential parameter controlling one-electron oxidation of Met. Mechanistic aspects of oxidation processes by various one-electron oxidants in various structural and pH environments are summarized and discussed. The importance of these studies for understanding oxidation of Met in real biological systems is also addressed.
甲硫氨酸（Met）的氧化是一种重要的反应，在氧化应激和衰老过程中的蛋白质修饰中起着关键作用。Met 氧化的第一步涉及到非常活跃和短暂的瞬态的产生。应用互补的时间分辨辐射和光化学技术（脉冲辐射解和激光闪光光解以及时间分辨 CIDNP 和 ESR 技术），可以详细比较由 OH 自由基和其他单电子氧化剂或敏化剂的激发三重态引发的单电子氧化机制，例如 4-，3-羧酸二苯甲酮。本综述的主要目的是介绍影响形成中间体性质的各种因素。它们分为两部分：与含 Met 的分子结构密不可分的部分和与外部因素相关的部分。前者包括（i）末端胺和羧基的保护，（ii）Met 在肽分子中的位置，（iii）除 Met 以外的相邻氨基酸的性质，（iv）肽链的性质（开环与闭环），（v）肽和蛋白质中 Met 残基的数量，以及（vi）Met 残基的光学异构体。外部因素包括氧化剂的类型、pH 值以及反应环境中含 Met 化合物的浓度。特别关注邻基参与，这是控制 Met 单电子氧化的一个重要参数。在各种结构和 pH 环境中，各种单电子氧化剂氧化过程的机制方面进行了总结和讨论。还讨论了这些研究对于理解真实生物系统中 Met 氧化的重要性。
