Molecular characterization and innate immune defense functional analysis of tartrate-resistant acid phosphatase 5 in Trachinotus ovatus

The enzyme tartrate-resistant acid phosphatase 5 (TRAP5) performs an important biological function in immune defense. In the present study, the TRAP5 of Trachinotus ovatus (golden pompano, TroTRAP5) was cloned to assess its biological function. The open reading frame of TroTRAP5 was 990 bp in length and its mature peptide encoded a 34.775-kDa protein that contained a metallophosphatase superfamily domain. Homology sequence alignment revealed that the similarity among teleost fish was 57.66 %–75.99 %. Meanwhile, phylogenetic tree analysis showed that TroTRAP5 was clustered into one branch with teleost TRAP5. TroTRAP5 expression was the most abundant in immune organs (liver, spleen, head kidney, and gills) and up-regulated during bacterial infection. Of note, purified recombinant TroTRAP5 (rTroTRAP5) exhibited phosphatase activity, and the optimal pH and temperature for its activity were 6.0 and 50 ℃. In vivo experiments indicated that TroTRAP5 overexpression in T. ovatus significantly reduced bacterial infection in fish tissues, whereas TroTRAP5 knockdown increased bacterial dissemination and colonization in fish tissues. In summary, the present study results suggest that TroTRAP5 participates in the antibacterial immune response.