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Plant glutathione peroxidases
Authors:Yuval Eshdat  Doron Holland  Zehava Faltin  Gozal Ben-Hayyim
Institution:Dept of Fruit Tree Breeding and Molecular Genetics, Agricultural Research Organization, The Volcani Center, 50250 Bet-Dagan, Israel.
Abstract:Oxidative stress in plants causes the induction of several enzymes, including superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2). The first two are responsible for converting superoxide to H2O2 and its subsequent reduction to H2O, and the third is involved in recycling of ascorbate. Glutathione peroxidases (GPXs, EC 1.11.1.9) are a family of key enzymes involved in scavenging oxyradicals in animals. Only recently, indications for the existence of this enzyme in plants were reported. Genes with significant sequence homology to one member of the animal GPX family, namely phospholipid hydroperoxide glutathione peroxidase (PHGPX), were isolated from several plants. Cit-SAP, the protein product encoded by the citrus csa gene, which is induced by salt-stress, is so far the only plant PHGPX that has been isolated and characterized. This protein differs from the animal PHGPX in its rate of enzymatic activity and in containing a Cys instead of selenocysteine (Sec) as its presumed catalytic residue. The physiological role of Cit-SAP and its homologs in other plants is not yet known.
Keywords:Citrus sinensis            oxidative stress  phospholipid hydroperoxide  plant glutathione peroxidases  selenocysteine
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