MOLECULAR, TRANSCRIPTIONAL AND FUNCTIONAL INSIGHTS OF ROCKFISH 1-CYS PEROXIREDOXIN

Peroxiredoxins are antioxidative enzymes that catalyze the reduction of alkyl hydroperoxides to alcohols and hydrogen peroxide to water. To characterize the peroxiredoxi 6 biochemical functions, 1-Cys Prx gene was cloned from Sebastes schlegelii (SsPrx6) and carried out the hydrogen peroxide reduction, DNA protection and oxidoreductase activities. Putative open reading frame encoded 221 amino acids with 25 kDa polypeptide and a pI of 5.6. A thioredoxin-2 domain and a Prx-specific signature motif were identified.Catalytic triad amino acids, N-linked glycosylation site and peroxidatic cysteine was identified. It shared the highest identity (93.2%) and similarity (98.2%) with the Cynoglossus semilaevis Prx6. Multiple sequence alignment revealed the conservation of functionally active peroxidatic cysteines and Prx-specific signature among the other Prx6 counterparts suggesting the common peroxidase activity. Viable cell number was increased by extracellular hydrogen peroxide scavenging activity of recombinant SsPrx6. Moreover, it could reduce the intracellular ROS level in THP-1 cells and zebrafish larvae via extracellular hydrogen peroxide scavenging activity of rSsPrx6. Metal catalyzed oxidative (MCO) stress, cleaved the pUC19 DNA from supercoiled state into nicked state where, rSsPrx6 protein could protect the pUC19 DNA cleavage by MCO system in a concentration dependent manner. The oxidoreductase activity of rSsPrx6 catalyzed the insulin reduction activity with the presence of 1,4-Dithiothreitol (DTT) in a time dependent manner. The SsPrx6 transcripts were ubiquitously expressed in all examined tissues with highest expression in ovary followed by testis. Bacterial (Streptococcus iniae and LPS) and viral (poly I:C) immune stimulated kidney and liver tissues showed significant SsPrx6 mRNA expression after the post infection. Collectively, SsPrx6 is belonging to the teleostean peroxiredoxin family member with its antioxidant function and potential immune responses upon bacterial and viral challenges. Also, it could be suggested that SsPrx6 is an active member of rockfish antioxidant and innate immune defense systems.