Plant peroxiredoxins: alternative hydroperoxide scavenging enzymes.

The role of plant peroxiredoxins in the detoxification systems is discussed in relation with the existence of many isoforms of this protein in distinct plant compartments. Phylogenetic analyses indicate that plant peroxiredoxins can be divided into four classes. Two of these classes correspond to chloroplastic enzymes. All isoforms contain at least one conserved catalytic cysteine. The enzymes belonging to the 1-Cys Prx class seem to be seed restricted and to play a role of detoxification during the germination process. At least one putative cytosolic isoform can use both thioredoxin and glutaredoxin as an electron donor, but the chloroplastic isoforms characterized depend on reduced thioredoxin. Mutagenesis and plant transformation studies support the proposal that the chloroplastic peroxiredoxins play an important role in combating the ROS species generated at the level of the chloroplastic electron transfer chain.