Molecular Characterization and Antibacterial Potential of Goose-Type Lysozyme from Japanese Pufferfish (Takifugu rubripes)

Lysozyme plays a crucial role in the innate immune response against bacterial phagocytosis by hydrolyzing the peptidoglycan layer of the bacterial cell wall. In this study, we characterized a goose-type lysozyme gene (TrLysG) in Japanese pufferfish. It is made up of an ORF of 573 bp that encodes a polypeptide of 190 amino acids. TrLysG includes a characteristic bacterial soluble lytic transglycosylase (SLT) domain, which contains three catalytic residues (Glu(71), Asp(84) and Asp(95)) and a highly conserved GLMQ motif (Gly(90), Leu(91), Met(92) and Gln(93)). Phylogenetic analyses revealed that TrLysG is clustered together with its counterparts from other teleost fishes. Furthermore, mRNA expression analyses showed that TrLysG was highly expressed in healthy mucosal tissues (intestines and gills), and considerably up-regulated in response to Vibrio harveyi infection in the intestines, gills, and liver. At pH 6 and 55 degrees C, the pure recombinant TrLysG (rTrLysG) exhibits optimum activity. It also displayed antimicrobial activity against three Gram-positive bacteria (Streptococcus parauberis, Staphylococcus pasteuri and Staphylococcus epidermidis) as well as five Gram-negative bacteria (Shewanella, Aeromonas hydrophila, Escherichia coli, Vibrio parahaemolyticus and V. harveyi). Our results highlighted the significant role of TrLysG in immune defense against invading pathogens, thereby contributing to the prevention and alleviation of disease spread in aquaculture.