Molecular cloning, mRNA expression and functional characterization of a catalase from Chinese black sleeper (Bostrychus sinensis)

In this study, the catalase gene of Chinese black sleeper Bostrychus sinensis (termed as BsCat) was sequenced and characterized. The BsCat, which encodes 525 amino acids, contains a catalase proximal active site signature domain ((64)FDRERIPERVVHAKGAG(80)) and a catalase proximal heme-ligand signature domain ((354)RLFAYPDTH(362)). The BsCat exhibits high sequence similarity with Cat of other species. Phylogenetic tree reconstruction revealed a close evolutionary relationship of BsCat to catalase genes of other fishes. The results of Real-time PCR showed that the BsCat gene was constitutively expressed in most organs of B. sinensis, with predominant expression detected in liver, followed by peripheral blood and spleen. Moreover, the BsCat gene was significantly changed after either poly (I:C) stimulation or Vibrio parahemolyticus infection in peripheral blood, head kidney, liver and spleen. The enzymatic activity of purified recombinant BsCat (rBsCat) was 2261 +/- 96 U/mg. The rBsCat exhibits optimum enzymatic activity at 15 degrees C and pH 7.0. Our results suggested that the BsCat is involved in the antioxidant defense and host immune response of Chinese black sleeper during pathogen invasion.