Studies on superoxide dismutase and oxidative stress response in fishes

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Cu, Zn-superoxide dismutase (Cu, Zn-SOD) activities were compared in Japanese flounder Paralichthys olivaceus for four different kinds of bacterial infections. A significant increase in Cu, Zn-SOD levels was recorded in hepato-pancreas at the initial stages of Edwardsiella tarda (E. tarda) infection. It was suggested that the remarkable change of Cu, Zn-SOD activities was a characteristic phenomenon of E. tarda.Cu, Zn-SOD and Mn-SOD were purified to homogeneity from Japanese flounder hepato-pancreas. On SDS-PAGE, the purified Cu, Zn-SOD and Mn-SOD gave single protein bands with molecular mass of 17.8 kDa and 26 kDa under reducing conditions, respectively. The N-terminal ammo acid sequences were determined for 25 amino acid residues (Cu, Zn-SOD) and 19 residues (Mn-SOD), the sequences were compared with other SODs. Reverse transcription-polymerase chain reaction of RNA from Japanese flounder hepato-pancreas was performed using primers designed according to the amino acid sequences determined, and we determined primary structure of Japanese flounder Cu, Zn-SOD and Mn-SOD. Furthermore, recombinant Cu, Zn-SOD (rCu, Zn-SOD) was expressed in Escherichia coli and was recovered as an active form.