An acidic phospholipase A₂ with antibacterial activity from Porthidium nasutum snake venom

Snake venoms are complex mixtures of proteins among which both basic and acidic phospholipases A(2) (PLA(2)s) can be found. Basic PLA(2)s are usually responsible for major toxic effects induced by snake venoms, while acidic PLA(2)s tend to have a lower toxicity. A novel PLA(2), here named PnPLA(2), was purified from the venom of Porthidium nasutum by means of RP-HPLC on a C18 column. PnPLA(2) is an acidic protein with a pI of 4.6, which migrates as a single band under both non-reducing and reducing conditions in SDS-PAGE. PnPLA(2) had a molecular mass of 15,802.6 Da, determined by ESI-MS. Three tryptic peptides of this protein were characterized by HPLC-nESI-MS/MS, and N-terminal sequencing by direct Edman degradation showing homology to other acidic PLA(2)s from viperid venoms. PnPLA(2) displayed indirect hemolytic activity in agarose erythrocyte-egg yolk gels and bactericidal activity against Staphylococcus aureus in a dose-dependent manner, with a MIC and MBC of 32 μg/mL. In addition, PnPLA(2) showed a potent inhibitory effect on platelet aggregation with doses up to 40 μg/mL. This acidic PLA(2), in contrast to basic enzymes isolated from other viperid snake venoms, was not cytotoxic to murine skeletal muscle myoblasts C(2)C(12). This is the first report on a bactericidal protein of Porthidium nasutum venom.