Saccharomyces cerevisiale cells have three Omega class glutathione S-transferases acting as 1-Cys thiol transferases
Saccharomyces cerevisiale cells have three Omega class glutathione S-transferases acting as 1-Cys thiol transferases
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DOI：
10.1042/bj20060034
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发表时间：
2006-09-01
影响因子：
4.1
通讯作者：
Herrero, Enrique
中科院分区：
文献类型：
--
作者：
Garcera, Ana;Barreto, Lina;Herrero, Enrique
酿酒酵母基因组编码三种蛋白质，它们与人谷胱甘肽S-转移酶（Omega class glutathione S-transferases）hGSTO 1 -1和hGSTO 2 -2具有相似性。这三种酵母蛋白被命名为Gto 1、Gto 2和Gto 3，它们的纯化重组形式作为巯基转移酶（谷氧还蛋白）对RED（β-羟乙基二硫化物）、脱氢抗坏血酸还原酶和二甲基胂酸还原酶具有活性，而它们对标准GST底物CDNB（1-氯2，4-二硝基苯）没有活性。它们的谷氧还蛋白活性也可在酵母细胞提取物中检测到。Gto蛋白的酶活性特征与另一种酵母GST Gtt 1的酶活性特征形成对比。后者对CDNB有活性，并且还显示出对有机氢过氧化物如氢过氧化枯烯的谷胱甘肽过氧化物酶活性，但作为硫醇转移酶没有活性。来自野生型Gto 2的点突变体的分析表明，在该分子的三个半胱氨酸残基中，只有位置46处的残基是谷氧还蛋白活性所需的。这表明巯基转移酶通过单巯基机制起作用。用所提出的含有Cys的Gto 2活性位点（46）替换酵母单硫醇谷氧还蛋白Grx 5的活性位点允许Grx 5保留一些针对HED的活性。因此，与Gto 2和Grx 5中相应的活性半胱氨酸残基相邻的残基是针对含二硫化物的小分子的巯基转移酶活性的重要决定因素。
The Saccharomyces cerevisiae genome encodes three proteins that display similarities with human GSTOs (Omega class glutathione S-transferases) hGSTO1-1 and hGSTO2-2. The three yeast proteins have been named Gto1, Gto2 and Gto3, and their purified recombinant forms are active as thiol transferases (glutaredoxins) against RED (beta-hydroxyethyl disulphide), as dehydroascorbate reductases and as dimethylarsinic acid reductases, while they are not active against the standard GST substrate CDNB (1-chloro2,4-dinitrobenzene). Their glutaredoxin activity is also detectable in yeast cell extracts. The enzyme activity characteristics of the Gto proteins contrast with those of another yeast GST, Gtt1. The latter is active against CDNB and also displays glutathione peroxidase activity against organic hydroperoxides such as cumene hydroperoxide, but is not active as a thiol transferase. Analysis of point mutants derived from wild-type Gto2 indicates that, among the three cysteine residues of the molecule, only the residue at position 46 is required for the glutaredoxin activity. This indicates that the thiol transferase acts through a monothiol mechanism. Replacing the active site of the yeast monothiol glutaredoxin Grx5 with the proposed Gto2 active site containing Cys(46) allows Grx5 to retain some activity against HED. Therefore the residues adjacent to the respective active cysteine residues in Gto2 and Grx5 are important determinants for the thiol transferase activity against small disulphide-containing molecules.