Biochemical characterization of LysVpKK5 endolysin from a marine vibriophage

Endolysins have been proposed as a potential antibacterial alternative for aquaculture, especially against Vibrio; the bacterial-agents that most frequently cause disease. Although multiple marine vibriophages have been characterized to date, research on vibriophage endolysins is recent. In this study, biochemical characterization of LysVpKK5 endolysin encoded by Vibrio parahaemolyticus-infecting VpKK5 phage was performed. In silico analysis revealed that LysVpKK5 possesses a conserved amidase_2 domain with a zinc-binding motif of high structural similarity to T7 lysozyme (RMSD = 0.107 angstrom). Contrary to expectations, the activity was inhibited with Zn2+ and was improved with other divalent cations, especially Ca2+. It showed optimal muralytic activity at pH 10, and curiously, no lytic activity at pH 7 was recorded. As for the thermal stability test, the optimal activity was recorded at 30 degrees C; the higher residual activity was recorded at 4 degrees C, and was lost at 50 degrees C. On the other hand, increasing NaCl concentrations reduced the activity gradually; the optimal activity was recorded at 50 mM NaCl. On the other hand, the enzymatic activity at 0.5 M NaCl was approx 30% and of approx 50% in seawater. LysVpKK5 endolysin exhibited a higher activity on V. parahaemolyticus ATCC-17802 strain, in comparison with AHPND + strains.

Automated summary

Endolysins have been proposed as potential antibacterial alternatives for aquaculture, especially against Vibrio species. In this study, the biochemical characterization of LysVpKK5 endolysin encoded by the VpKK5 phage infecting Vibrio parahaemolyticus was conducted. The enzyme displayed unexpected activity patterns under different conditions, such as inhibition by Zn2+ and optimal muralytic activity at pH 10.