Glutathione peroxidase from the white shrimp Litopenaeus vannamei: characterization and its regulation upon pH and Cd exposure.

Glutathione peroxidase (GPx) is a key enzyme of cellular detoxification systems that defend cells against reactive oxygen species. Knowledge of the complement of GPx in shrimp is essential to understanding regulation and detoxification mechanisms of environmental stress. In this study, we expressed GPx from white shrimp Litopenaeus vannamei in Escherichia coli, and then characterized the purified recombinant enzyme with respect to the effects of pH, temperature on its catalytic activity. Quantitative real-time PCR and western blot analysis were carried out to investigate the expression patterns of GPx in shrimp hepatopancreas exposed to Cd stress. A statistically significant increase in expression of GPx mRNA and protein was observed in the Cd stress at 24 h. By contrast, western blot showed a significant up-regulation in GPx protein expression at 12 h exposed pH stress (5.6 and 9.3, respectively). These results suggest that L. vannamei GPx expression was modulated by Cd and pH stress and may play an important role in detoxification of xenobiotics and antioxidant defense. We conclude that GPx could be used as biomarkers of Cd and pH stress in aquatic environment for the studied species.