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Peroxiredoxin (Prx), also named thioredoxin peroxidase (TPx), is a selenium independent antioxidant enzyme that can protect organisms from oxidative damage caused by reactive oxygen species (ROS) and is important for immune responses. In this study, the molecular cloning and characterization of a Prx2 homologue (CiPrx2) were described from grass carp (Ctenopharyngodon idella). The full-length cDNA of CiPrx2 was 1163 bp containing 5ʹ-untranslated region (UTR) of 52 bp, a 3′-UTR of 517 bp with the putative polyadenylation consensus signal (AATAAA), an open reading frame (ORF) of 594 bp encoding polypeptides of 197 amino acids with a predicted molecular mass of 21.84 kDa and theoretical isoelectric point of 5.93. The analysis results of multiple sequence alignment and phylogenetic tree confirmed that CiPrx2 belong to the typical 2-Cys Prx subfamily. The CiPrx2 mRNA was ubiquitously expressed in all tested tissues. The temporal expression of CiPrx2 were differentially induced infected with grass carp reovirus (GCRV), polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharide (LPS) in liver and spleen. Subcellular localization of CiPrx2-GFP fusion proteins were only distributed in the cytoplasm. The purified recombinant CiPrx2 possessed an apparent antioxidant activity and could protect DNA against oxidative damage. Finally, CiPrx2 proteins could obviously inhibit H 2 O 2 and heavy metal toxicity. However, further researches are needed to better understand the regulation of CiPrx2 under oxidative stresses. • The molecular cloning and characterization of a Prx2 homologue (CiPrx2) were described from grass carp. • The CiPrx2 mRNA was ubiquitously expressed in the various tissues. • CiPrx2 was likely to be involved in the immune response against viral and bacterial infection. • Subcellular localization of CiPrx2-GFP fusion protein were only distributed in the cytoplasm. • CiPrx2 proteins could obviously inhibit H 2 O 2 and heavy metal toxicity and protect DNA against oxidative damage. [ABSTRACT FROM AUTHOR]