Plant glutathione peroxidases: Structural and functional characterization, their roles in plant development

Abstract

Glutathione peroxidase (GPX) enzymes (EC 1.11.1.9, EC 1.11.1.12 and EC 1.11.1.15) are widespread among eukaryotic organisms and have pivotal role in peroxide detoxification. Detailed phylogenetic analysis of thiol peroxidases, including eukaryotic peroxiredoxins (PRXs) and eukaryotic GPXs, has revealed that plant glutathione peroxidases are more closely related to mammalian hydroperoxide peroxidases than to fungal GPXs, and a more precise name for them should be glutathione peroxidase-like (GPXL) enzymes. Plant GPXLs are mostly monomeric proteins that use the thioredoxin (TRX) system more effectively than the glutathione system during the reduction of H2O2 and lipid peroxides. GPXLs were suggested to be a putative link between the glutathione-based and the thioredoxin-based detoxifying systems. They possess some functional overlaps with the PRXs and glutathione transferases (GSTs), with respect to the maintenance of H2O2 homeostasis by the elimination of peroxides, and are also involved in the regulation of the redox homeostasis by maintaining the thiol-disulfide balance. In addition GPXs have been shown to perform other functions, including acting as redox transducers in abscisic acid (ABA) regulated responses, drought stress signaling, and redox-associated modification of nuclear proteins. Plant GPXLs not only protect cells from stress-induced oxidative damage, but they have also implicated in the regulation of processes associated with plant growth and development. Among these processes, their involvement in plant regeneration and shoot organogenesis is discussed.