RESUMO
Glutathione S-transferases (GSTs) and glutathione peroxidases (GPxs) are essential components of cellular detoxification systems that defend cells against reactive oxygen species (ROSs). Two GSTgenes have recently been cloned from Fenneropenaeus chinensis and BLAST P analysis shows that one GST, designated FcMuGST, is similar to members of MuGST while the other has similarities to ThetaGST (FcThetaGST). A selenium-dependent glutathione peroxidase (Se-GPx) has also been cloned from F. chinensis. The alignment of the deduced GST and GPx amino acid sequences with those from other species showed that the residues essential for enzymatic function of these three proteins are highly conserved. Tissue distribution and response to pathogens for the three genes was investigated by RT-PCR analysis, which showed that the transcript of FcMuGST and FcGPx increased in response to Vibrio anguillarum infection, while FcThetaGST showed little change at the transcript level. GPx activity in gill tissues quickly increased at 6 h after V. anguillarum challenge and maintained at a relatively high level from 6 h to 24 h. Total GST activity in hepatopancreas and intestines of the bacterial challenged shrimp was increased at 6 h, and gradually recovered from 12 and 24 h to the normal level. These three genes were all predicted to play an important role in detoxification defense reactions. FcMuGST primarily scavenges excess ROS produced after bacterial infection, while clearance of endogenous hydrophobic electrophile molecules was mainly dependent on activities of FcThetaGST.