The Antimicrobial Activity of an Acidic Phospholipase A2 (NN-XIa-PLA2) from the Venom of Naja naja naja (Indian Cobra)

Microbial resistance against antibiotics is considered as a potentially serious threat to public health. Therefore, there is much interest in developing new molecules with novel modes of action. In this study, when antimicrobial potential of an acidic protein—NN-XIa-PLA2 (Naja naja venom phospholipase A2 fraction—XIa) of N. naja venom was evaluated, it demonstrated potent bactericidal action against the human pathogenic strains. It inhibited more significantly, the gram-positive bacteria, when compared to gram-negative bacteria. The minimum inhibitory concentration (MIC) values ranged from 17 to 20 μg/ml. It was interesting to observe that the NN-XIa-PLA2 showed comparable antibacterial activity to the standard antibiotics used. It was found that there was a strong correlation between phospholipase A2 (PLA2) activities, hemolytic, and antimicrobial activity. Further, it is found that in the presence of p-bromophenacyl bromide (p-BPB), there is a significant decrease in enzymatic activity and associated antimicrobial activities, suggesting that a strong correlation exists between catalytic activity and antimicrobial effects, which thereby destabilize the membrane bilayer. However, other mechanisms cannot be completely ruled out. Thus, these studies encourage further in-depth study on molecular mechanisms of antibacterial properties and thereby help in development of this protein into a possible therapeutic lead molecule for treating bacterial infections.