A novel bactericidal homodimeric PLA2 group-I from Walterinnesia aegyptia venom

Abstract

A novel non-toxic phospholipase A2 was purified to homogeneity in a single chromatography step from the venom of Walterinnesia aegyptia, a monotypic elapid snake caught in Saudi Arabia, and its antimicrobial and hemolytic properties were evaluated as well. This enzyme, namely WaPLA2, is a homodimer with an estimated molecular mass of 30 kDa, and its NH2-terminal sequence exhibits a significant degree of similarity with PLA2 group-I. At optimal pH (8.5) and temperature (45 °C), the purified PLA2 exhibited a specific activity of 2100 U/mg, and it requires bile salts and Ca2+ for its activity. However, other cations such as Cd2+ and Hg2+ diminished the enzyme activity remarkably, thereby suggesting that the catalytic site arrangement has an exclusive structure for Ca2+ binding. Furthermore, WaPLA2 maintained almost 100% and 60% of its full activity in a pH range of 6.0–10 after 24 h incubation or after 60 min treatment at 70 °C, respectively. In the biological activity assays, WaPLA2 displayed potent indirectly hemolytic and antimicrobial activities that were strongly correlated. These promising findings encourage further in-depth research to understand the molecular mechanism of WaPLA2's antimicrobial properties for its possible use as a potential therapeutic lead molecule for treating infections.