These ROS are highly reactive molecules that are capable of damaging cellular constituents such as DNA, RNA, lipids and proteins [16]. In adaptation to oxidative

stress, aerobic organisms have evolved multiple enzymatic and non-enzymatic defense systems to protect their cellular constituents from ROS and to maintain their cellular redox state [17]. Accumulation of ROS is known to increase under many, if not all, stress conditions as the defensive scavenging systems become insufficient to cope with increasing levels of stress. The enzymatic scavenging system for ROS involves a number of enzyme-catalyzed reactions in different cellular compartments. A series of peroxidases referred to as peroxiredoxins (Prxs) that see more selleck screening library are ancestral thiol-dependent selenium- and heme-free peroxidases [18] have been found from archaea, lower prokaryotes to higher eukaryotes. These peroxidases constitute a large family including bacterial AhpC proteins and eukaryotic thioredoxin peroxidases (TPxs) [19]. Prxs are abundant, well-distributed

peroxidases that reduce H2O2, organic peroxides and peroxynitrite at the expense of thiol compounds. Thus, Prxs are considered alternative hydroperoxide scavenging enzymes, as they can reduce both organic and inorganic peroxides as well as oxidized enzymes. Based on the number of cysteine residues involved in catalysis, Prxs can be divided into three classes: typical 2-Cys Prxs, atypical 2-Cys prxs and 1-Cys Prxs [20]. Prxs are ubiquitous proteins that use an active site Cys residue from one of the homodimers to reduce H2O2. The peroxidative cysteine sulfenic acid Methane monooxygenase formed upon reaction with peroxide is reduced directly by glutathione. It is suggested that Prxs can act alternatively as peroxidases or as molecular chaperones by changing their molecular complexes. Furthermore, the oxidized cysteinly species, cysteine sulfenic acid, may play a dual

role by acting as a catalytic intermediate in the peroxidase activity and as a redox sensor in regulating H2O2-mediated cell defense signaling. Alkyl hydroperoxide reductase (Ahp) is the second known member of a class of disulfide oxidoreductases [21] and a member of the thiol-dependent peroxiredoxin family [20], which possesses activity against H2O2, organic peroxides, and peroxynitrite [22]. Therefore, expression of Ahp genes plays an important role in peroxide resistance (oxidative stress) in Bacillus subtilis [23], Clostridium pasteurianum [24] and Burkholderia cenocepacia [25]. Moreover, the compensatory expression of AhpC in Burkholderia pseduomallei katG is essential for its resistance to reactive nitrogen intermediates [26]. In this article, we report the isolation of DhAHP from the extreme halophilic yeast D. hansenii via subtractive hybridization of cDNA isolated from high salt treated vs. non-treated cells.