Characterization of a mammalian peroxiredoxin that contains one conserved cysteine
Characterization of a mammalian peroxiredoxin that contains one conserved cysteine
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DOI：
10.1074/jbc.273.11.6303
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发表时间：
1998-03-13
影响因子：
4.8
通讯作者：
Rhee, SG
中科院分区：
文献类型：
--
作者：
Kang, SW;Baines, IC;Rhee, SG
最近发现了一种新型的过氧化物酶，称为硫氧还蛋白过氧化物酶(TPX)，它利用硫氧还蛋白产生的电子还原H_2O_2，并含有两种必需的半胱氨酸。TPX同源物，称为过氧化还蛋白(PRX)，也已被鉴定，并包括几个蛋白质，命名为1-Cys PRX，只含有一个保守的半胱氨酸，在大肠杆菌中表达和纯化的重组人1-Cys PRX现在被证明可以通过二硫苏糖醇提供的电子还原H_2O_2。此外，在NIH3T3细胞中瞬时表达的人1-Cys PRX能够清除细胞内因外源过氧化氢或血小板衍生生长因子处理而产生的过氧化氢。保守的Cys(47)-SH基团是H_2O_2氧化的中心。因此，Cys(47)突变为丝氨酸使过氧化物酶活性丧失。此外，氧化的中间体似乎是Cys-SOH。与TPX不同的是，两个保守的半胱氨酸中的一个被氧化成Cys-SOH，然后立即与酶同源二聚体第二亚单位的第二个保守的半胱氨酸反应，形成分子间二硫键，而1-Cys Prx的Cys-SOH不形成二硫键。还原TPX二硫键的硫氧还蛋白和降低氧化谷胱甘肽过氧化物酶活性的谷胱甘肽都不能降低1-Cys PRX的Cys-SOH，因此不能支持过氧化物酶的活性。人的1-Cys Prx在酸性条件下表现出低水平的磷脂酶A(2)活性，因此该酶被认为是溶酶体，Ser(32)被认为是脂肪酶功能的关键。然而，Ser(32)或Cys(47)的突变现已被证明对1-Cys Prx的脂肪酶活性没有影响，1-Cys Prx也被证明是一种胞质蛋白。因此，1-Cys Prx的主要细胞功能似乎是利用尚未确定的来源提供的电子来还原过氧化物酶；因此，该酶代表了一种新的过氧化物酶。
A new type of peroxidase enzyme, named thioredoxin peroxidase (TPx), that reduces H2O2 with the use of electrons from thioredoxin and contains two essential cysteines was recently identified. TPx homologs, termed peroxiredoxin (Prx), have also been identified and include several proteins, designated 1-Cys Prx, that contain only one conserved cysteine, Recombinant human 1-Cys Prx expressed in and purified from Escherichia coli has now been shown to reduce H2O2 with electrons provided by dithiothreitol. Furthermore, human 1-Cys Prx transiently expressed in NIH 3T3 cells was able to remove intracellular H2O2 generated in response either to the addition of exogenous H2O2 or to treatment with platelet-derived growth factor. The conserved Cys(47)-SH group was shown to be the site of oxidation by H2O2. Thus, mutation of Cys(47) to serine abolished peroxidase activity. Moreover, the oxidized intermediate appears to be Cys-SOH. In contrast to TPx, in which one of the two conserved cysteines is oxidized to Cys-SOH and then immediately reacts with the second conserved cysteine of the second subunit of the enzyme homodimer to form an intermolecular disulfide, the Cys-SOH of 1-Cys Prx does not form a disulfide. Neither thioredoxin, which reduces the disulfide of TPx, nor glutathione, which reduces the Cys-SeOH of oxidized glutathione peroxidase, was able to reduce the Cys-SOH of 1-Cys Prx and consequently could not support peroxidase activity. Human 1-Cys Prx was previously shown to exhibit a low level of phospholipase A(2) activity at an acidic pH; the enzyme was thus proposed to be lysosomal, and Ser(32) was proposed to be critical for lipase function. However, the mutation of Ser(32) or Cys(47) has now been shown to have no effect on the lipase activity of 1-Cys Prx, which was also shown to be a cytosolic protein. Thus, the primary cellular function of 1-Cys Prx appears to be to reduce peroxides with the use of electrons provided by an as yet unidentified source; the enzyme therefore represents a new type of peroxidase.