The Peroxiredoxin and Glutathione Peroxidase Families in Chlamydomonas reinhardtii

Abstract

Thiol/selenol peroxidases are ubiquitous nonheme peroxidases. They are divided into two major subfamilies: peroxiredoxins (PRXs) and glutathione peroxidases (GPXs). PRXs are present in diverse subcellular compartments and divided into four types: 2-cys PRX, 1-cys PRX, PRX-Q , and type II PRX (PRXII). In mammals, most GPXs are selenoenzymes containing a highly reactive selenocysteine in their active site while yeast and land plants are devoid of selenoproteins but contain nonselenium GPXs. The presence of a chloroplastic 2-cys PRX, a nonselenium GPX, and two selenium-dependent GPXs has been reported in the unicellular green alga Chlamydomonas reinhardtii. The availability of the Chlamydomonas genome sequence offers the opportunity to complete our knowledge on thiol/selenol peroxidases in this organism. In this article, Chlamydomonas PRX and GPX families are presented and compared to their counterparts in Arabidopsis, human, yeast, and Synechocystis sp. A summary of the current knowledge on each family of peroxidases, especially in photosynthetic organisms, phylogenetic analyses, and investigations of the putative subcellular localization of each protein and its relative expression level, on the basis of EST data, are presented. We show that Chlamydomonas PRX and GPX families share some similarities with other photosynthetic organisms but also with human cells. The data are discussed in view of recent results suggesting that these enzymes are important scavengers of reactive oxygen species (ROS) and reactive nitrogen species (RNS) but also play a role in ROS signaling. L IFE in an oxygen-rich environment has to deal with the danger of oxidative stress. During normal cell metabolism, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are constantly produced, essentially by respiratory and photosynthetic electron transfer chains. These highly reactive molecules can react with many cell components and damage DNA, proteins, and lipids. Thus, their concentration has to be strictly controlled. For this purpose, aerobic organisms are equipped with nonenzymatic (ascorbate, glutathione, tocopherol, and carotenoid) or enzymatic (catalase, ascorbate peroxidase, superoxide dismutase, glutathione peroxidase, and peroxiredoxin) antioxidant systems to remove ROS from the cells. To control their concentrations, ROS and RNS have to be sensed. It has been established in many organisms that ROS, and especially hydrogen peroxide, are signaling molecules that diffuse across membranes and induce specific signal transduction pathways. Furthermore, ROS can also be produced on purpose by cells in response to several stimuli to function as second messengers inside the cell. Finally, ROS and RNS can control enzyme activities by triggering several post-translational modifications such as disulfide bond formation, thiol oxidation to sulfenic/sulfinic/sulfonic acid, glutathionylation, nitrosylation, or carbonylation.Thiol/selenol peroxidases have emerged, during recent years, as important scavengers of ROS/RNS but they ...

Systems-Wide Analysis of Acclimation Responses to Long-Term Heat Stress and Recovery in the Photosynthetic Model OrganismChlamydomonas reinhardtii

“…An HCP ortholog in E. coli was shown to be specifically induced by H 2 O 2 and to confer protection toward hydrogen peroxide (Almeida et al, 2006). Moreover, three peroxiredoxins, PRX1, PRX2, and PRX4, targeted to chloroplast, cytosol, and mitochondria, respectively (Dayer et al, 2008), were upregulated 1.2-fold. Also, thioredoxins TRXm and TRXh1, and ferredoxin-thioredoxin reductase (FRR2), most likely involved in the regeneration of oxidized peroxiredoxins in the respective compartments (Dietz et al, 2006), were upregulated 1.2-to 1.9-fold after 24 h of HS.…”

In situ dynamics of O2, pH and cyanobacterial transcripts associated with CCM, photosynthesis and detoxification of ROS

“…Photoinhibition, a consequence of photodamage to photosystem II, can lead to a further rise of ROS levels. Oxidative stress in phototrophs can be alleviated by the synthesis of various enzymes (for example, glutathione peroxidase, glutathione S-transferases, thioredoxins and superoxide dismutase) that help minimize ROSelicited damage (Goyer et al, 2002;Sarkar et al, 2005;Dayer et al, 2008). Harmful effects of light on phototrophs will also depend on Ci availability, as well as on environmental levels of other nutrients, for example, nitrogen, phosphorus, sulfur and iron (Takahashi and Murata, 2008).…”

Effect of foliar application of selenium on the content of selected amino acids in potato tubers (Solanum tuberosum L.)

“…However, no Se-containing GSH-Px was identified in plants, in contrast to animals (Dayer et al 2008, Ríos et al 2009). Seppänen et al (2003) discovered that Se reduced the activity of superoxide dismutase (SOD) and in some cases the amount of tocopherols.…”