Glutathione reductase is an antioxidant enzyme which is able to convert oxidized glutathione (GSSG) into reduced glutathione (GSH) to maintain the GSH/GSSG level of the cells during the oxidative stress. Reactive oxygen and nitrogen species such as super oxide radicals, hydroxyl radicals, hydrogen peroxide and nitrogen oxide molecules cause for the oxidative stress in most aerobic organisms. Glutathione (GSH) is the major intracellular thiol compound can find in organs such as endoplasmic reticulum, nucleus and mitochondria. In this study we characterized structural and functional features of the mitochondrial glutathione reductase gene (HaGSR) of seahorse.
The identified cDNA sequence of HaGSR was 1467 bp long and consist of 1398 bp long open reading frame (ORF). The HaGSR protein composed with 465 amino acids with molecular weight of 50.14 KDa and calculated theoretical pI of 7.63. Also, the HaGSR protein contains typical GSR structural features, including NADPH binding site (184-189 aa), FAD binding domain (14-32 aa) and glutathione binding site (45-55 aa). Glutathione reductase mitochondrial isoform 3 gene of Fundulus heteroliticus showed the highest 82.9 % identity and 91.1 % similarity with HaGSR. According to the phylogenetic analysis HaGSR showed close relationship with teleost fish.
Ovaries showed the highest expression for tissue specific distribution among fourteen tissues of seahorse. The mRNA expression profiles of HaGSR in blood and liver displayed significant inductions after the immune challenge mounted by Lipopolysaccharides (LPS), polyinosinic:polycytidylic acid (Poly I:C), Edwardsiella tarda and Streptococcus iniae. According to the results all the stimuli showed symbolic response at 48 h and 72 h post infection in both tissues. Altogether, these results suggest that the HaGSR might play an important protective role in seahorse against invading pathogens.