Plant peroxiredoxins: catalytic mechanisms, functional significance and future perspectives.

Peroxiredoxins (Prx) are a family of thiol dependent peroxidases found in almost all kingdoms. In plants, five major classes of Prx are known. They are known to catalyze the decomposition of peroxides and as they lack a prosthetic group, the catalytic cycle results in the generation of an inactive form of Prx. In order to regain the active form, Prx rely on external electron donors such as thioredoxins, glutaredoxins, cyclophilins, NADPH-dependent thioredoxin reductase C (NTRC) etc. In addition to their well established role in antioxidative defense, Prx are also reported to play an important role in growth and development, dessication tolerance in dormant seeds, protection of photosynthesis, defense against pathogens and redox signaling. Prx are also known to establish an alternate water-water cycle for the detoxification of H₂O₂, parallel to ascorbate-dependent H₂O₂ detoxification. But the relative contribution of Prx in detoxifying H₂O₂ compared to ascorbate peroxidase is not known so far due to experimental limitations. In view of the above, the present review focuses on the recent developments on Prxs.