Differing views of the role of selenium in thioredoxin reductase.
Differing views of the role of selenium in thioredoxin reductase.
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DOI：
10.1007/s00726-010-0494-6
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发表时间：
2011-06
期刊：
影响因子：
3.5
通讯作者：
Ruggles, Erik L.
中科院分区：
文献类型：
--
作者：
Hondal, Robert J.;Ruggles, Erik L.
本文综述了哺乳动物硫氧还蛋白还原酶活性位点中硒以硒代半胱氨酸形式存在的三种不同的化学解释。这些意见如下：（1）传统观点认为，硒代半胱氨酸是相对于半胱氨酸的上级亲核试剂，（2）由于硒醇的pKa显着较低，因此其相对于硫醇的上级离去基团能力，以及（3）相对于硫，硒接受电子的上级能力（亲电子性）。我们将这些化学解释称为硒在酶中的“化学-酶促”功能。我们正式定义硒的化学-酶功能为它的特定化学性质，允许硒酶催化其单独的反应。然而，我们和其他人质疑硒代半胱氨酸是否是催化酶促反应所必需的化学物质，因为含硒代半胱氨酸的酶的半胱氨酸同系物以高催化效率催化其特异性酶促反应。酶中硒代半胱氨酸的存在一定有独特的化学原因，这解释了基因组上维持复杂的硒代半胱氨酸插入机制的生物压力。我们将这种生物压力称为硒代半胱氨酸的“化学-生物”功能。我们讨论的证据表明，这种化学-生物学功能是硒酶抵抗不可逆氧化失活的能力。硒代半胱氨酸赋予抗氧化性的方式可能是由于硒代半胱氨酸的氧化形式（Sec-SeO 2 −，硒酸）与半胱氨酸-亚磺酸到半胱氨酸（Cys-SO2−到Cys-SH）的相同循环相比，其上级再循环回到其母体形式（Sec-SeH，硒代半胱氨酸）的能力更强。
This review covers three different chemical explanations that could account for the requirement of selenium in the form of selenocysteine in the active site of mammalian thioredoxin reductase. These views are the following: (1) the traditional view of selenocysteine as a superior nucleophile relative to cysteine, (2) the superior leaving group ability of a selenol relative to a thiol due to its significantly lower pKa and, (3) the superior ability of selenium to accept electrons (electrophilicity) relative to sulfur. We term these chemical explanations as the “chemico-enzymatic” function of selenium in an enzyme. We formally define the chemico-enzymatic function of selenium as its specific chemical property that allows a selenoenzyme to catalyze its individual reaction. However we, and others, question whether selenocysteine is chemically necessary to catalyze an enzymatic reaction since cysteine-homologs of selenocysteine-containing enzymes catalyze their specific enzymatic reactions with high catalytic efficiency. There must be a unique chemical reason for the presence of selenocysteine in enzymes that explains the biological pressure on the genome to maintain the complex selenocysteine-insertion machinery. We term this biological pressure the “chemico-biological” function of selenocysteine. We discuss evidence that this chemico-biological function is the ability of selenoenzymes to resist inactivation by irreversible oxidation. The way in which selenocysteine confers resistance to oxidation could be due to the superior ability of the oxidized form of selenocysteine (Sec-SeO2−, seleninic acid) to be recycled back to its parent form (Sec-SeH, selenocysteine) in comparison to the same cycling of cysteine-sulfinic acid to cysteine (Cys-SO2− to Cys-SH).
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影响因子：
3.7
作者：
Anestål K;Prast-Nielsen S;Cenas N;Arnér ES
通讯作者：
Arnér ES
DOI：
10.1093/protein/gzg088
发表时间：
2003-09-01
期刊：
PROTEIN ENGINEERING
影响因子：
--
作者：
Carugo, O;Cemazar, M;Pongor, S
通讯作者：
Pongor, S
影响因子：
2.6
作者：
Coles, Martyn P.
通讯作者：
Coles, Martyn P.
影响因子：
4.8
作者：
Cheng, Qing;Sandalova, Tatyana;Arner, Elias S. J.
通讯作者：
Arner, Elias S. J.
影响因子：
3.9
作者：
Assmann, A;Briviba, K;Sies, H
通讯作者：
Sies, H