Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy.
Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, the Netherlands; Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
Redox Biol. 2020 Jul;34:101540. doi: 10.1016/j.redox.2020.101540. Epub 2020 Apr 14.
The (seleno)cysteine residues in some protein families react with hydroperoxides with rate constants far beyond those of fully dissociated low molecular weight thiol or selenol compounds. In case of the glutathione peroxidases, we could demonstrate that high rate constants are achieved by a proton transfer from the chalcogenol to a residue of the active site [Orian et al. Free Radic. Biol. Med. 87 (2015)]. We extended this study to three more protein families (OxyR, GAPDH and Prx). According to DFT calculations, a proton transfer from the active site chalcogenol to a residue within the active site is a prerequisite for both, creating a chalcogenolate that attacks one oxygen of the hydroperoxide substrate and combining the delocalized proton with the remaining OH or OR, respectively, to create an ideal leaving group. The "parking postions" of the delocalized proton differ between the protein families. It is the ring nitrogen of tryptophan in GPx, a histidine in GAPDH and OxyR and a threonine in Prx. The basic principle, however, is common to all four families of proteins. We, thus, conclude that the principle outlined in this investigation offers a convincing explanation for how a cysteine residue can become peroxidatic.
某些蛋白质家族中的（硒）半胱氨酸残基与过氧化物氢的反应速率常数远远超过完全离解的低分子量硫醇或硒醇化合物。以谷胱甘肽过氧化物酶为例，我们可以证明，通过从硫醇转移质子到活性位点的残基，可以实现高反应速率常数[Orian 等人，《自由基生物学与医学》87（2015）]。我们将这项研究扩展到另外三个蛋白质家族（OxyR、GAPDH 和 Prx）。根据 DFT 计算，从活性位点的硫醇转移质子到活性位点内的残基是两者的先决条件，这会形成一种硫代酸盐，攻击过氧化物底物的一个氧原子，并将离域质子与剩余的 OH 或 OR 结合，分别形成理想的离去基团。在不同的蛋白质家族中，离域质子的“停泊位置”不同。在 GPx 中是色氨酸的环氮、GAPDH 和 OxyR 中的组氨酸以及 Prx 中的苏氨酸。然而，基本原则对于所有这四种蛋白质家族都是通用的。因此，我们得出结论，本研究中概述的原理为半胱氨酸残基如何成为过氧化物酶提供了令人信服的解释。
