Characterization of peroxiredoxin genes in Haematococcus pluvialis

Abstract

Peroxiredoxin (Prxs) are thiol-specific antioxidant protein. Prxs exert their protective antioxidant role in cells through their peroxidase activity (ROOH + 2e- ? ROH + H2O), whereby hydrogen peroxide, peroxynitrate, and a wide range of organic hydroperoxides(ROOH) are reduced and detoxified. In this study, we cloned 3 different Prx genes of Haematococcus pluvialis, and investigated their antioxidant characteristics. Prx2 in Haematococcus, which is the most highly homologous to 2-Cys-Prx(2-CP),was up regulated under astaxanthin induction stress conditions. This gene product is supposed to be localized in the chloroplast where is the site of most active oxygen metabolism in light. Under stress conditions such as high light, the photosynthetic reduction of O2 through the Mehler reaction results in the formation of free superoxide radials. Antioxidant defense mechanisms remove excess O2- and H2O2. Superoxide dismutase enzymes(SODs) remove O2- by accelerating its conversion to H2O2. Then, the hydrogen peroxide is removed by the ascorbate peroxidase, as described in the Mehler peroxidase reation. However, under severe stress the Mehler peroxidase reaction is not sufficient; thereby, the 2-CP-dependent alternative metabolic pathway to detoxify H2O2 was proposed.