Zaffagnini Mirko, Michelet Laure, Massot Vincent, Trost Paolo, Lemaire Stéphane D
Institut de Biotechnologie des Plantes, UMR 8618, CNRS/University of Paris-Sud 11, Bâtiment 630, Orsay 91405, Cedex, France.
J Biol Chem. 2008 Apr 4;283(14):8868-76. doi: 10.1074/jbc.M709567200. Epub 2008 Jan 23.
Glutaredoxins (GRXs) are small ubiquitous disulfide oxidoreductases known to use GSH as electron donor. In photosynthetic organisms, little is known about the biochemical properties of GRXs despite the existence of approximately 30 different isoforms in higher plants. We report here the biochemical characterization of Chlamydomonas GRX1 and GRX3, the major cytosolic and chloroplastic isoforms, respectively. Glutaredoxins are classified on the basis of the amino acid sequence of the active site. GRX1 is a typical CPYC-type GRX, which is reduced by GSH and exhibits disulfide reductase, dehydroascorbate reductase, and deglutathionylation activities. In contrast, GRX3 exhibits unique properties. This chloroplastic CGFS-type GRX is not reduced by GSH and has an atypically low redox potential (-323 +/- 4 mV at pH 7.9). Remarkably, GRX3 can be reduced in the light by photoreduced ferredoxin and ferredoxin-thioredoxin reductase. Both GRXs proved to be very efficient catalysts of A(4)-glyceraldehyde-3-phosphate dehydrogenase deglutathionylation, whereas cytosolic and chloroplastic thioredoxins were inefficient. Glutathionylated A(4)-glyceraldehyde-3-phosphate dehydrogenase is the first physiological substrate identified for a CGFS-type GRX.
谷氧还蛋白（GRXs）是一类普遍存在的小分子二硫键氧化还原酶，已知其以谷胱甘肽（GSH）作为电子供体。在光合生物中，尽管高等植物中存在约30种不同的异构体，但关于GRXs的生化特性却知之甚少。我们在此报告衣藻GRX1和GRX3的生化特性，它们分别是主要的胞质和叶绿体异构体。谷氧还蛋白根据活性位点的氨基酸序列进行分类。GRX1是典型的CPYC型GRX，可被GSH还原，并具有二硫键还原酶、脱氢抗坏血酸还原酶和去谷胱甘肽化活性。相比之下，GRX3具有独特的特性。这种叶绿体CGFS型GRX不能被GSH还原，且具有非典型的低氧化还原电位（在pH 7.9时为-323±4 mV）。值得注意的是，GRX3在光照下可被光还原的铁氧还蛋白和铁氧还蛋白-硫氧还蛋白还原酶还原。两种GRX均被证明是3-磷酸甘油醛脱氢酶去谷胱甘肽化的高效催化剂，而胞质和叶绿体硫氧还蛋白则效率较低。谷胱甘肽化的3-磷酸甘油醛脱氢酶是首个被鉴定的CGFS型GRX的生理底物。
