Molecular identification and biochemical characteristics of a delta class glutathione S-transferase gene (FcδGST) from Chinese shrimp Fenneropenaeus chinensis

Glutathione S-transferases (GSTs) are a superfamily of multifunction enzymes involved in the regulation of redox homeostasis and innate immune responses against various pathogenic infections in marine invertebrates. In the present study, a delta class GST gene (designated as Fc delta GST) was cloned from Fenneropenaeus chinensis using rapid amplification of cDNA ends (RACE) technology. The complete cDNA sequence of Fc delta GST was 780 bp in length, which includes a 27-bp 5 ' non-coding region (UTR), a 117-bp 3 ' UTR, a 636-bp open reading frame (ORF), and a polyadenylate signal site (AATAAA) presented at the upstream of poly A tail. The Fc delta GST gene encoded 211 amino acids peptide, including a GST_N domain and a GST_C domain, and exhibited high similarity with previously reported delta GSTs. The predicted molecular mass of Fc delta GST protein was 23.39 kDa, and its theoretical isoelectric point (pI) was 5.34. The Fc delta GST mRNA transcripts were ubiquitously expressed in all the tested tissues, with the highest expression level in hemocytes and hepatopancreas. During the stimulation of Vibrio anguillarum or white spot syndrome virus (WSSV), the mRNA expression of Fc delta GST in hemocytes and hepatopancreas revealed significant up-regulation. The purified recombinant Fc delta GST protein (designated as rFc delta GST) exhibited specific catalytic activity against 1-chloro-2, 4-dinitrobenzene (CDNB) substrate with relatively low stable enzymatic activities. These results indicated that Fc delta GST was a fragile but typical novel delta class GST member and potentially involved in the innate immune responses of F. chinensis.