Cytotoxic activities of [Ser ]phospholipase A2 from the venom of the saw-scaled vipers Echis ocellatus, Echis pyramidum leakeyi, Echis carinatus sochureki, and Echis coloratus

摘要

Fractionation by reversed-phase HPLC of venom from four species of saw-scaled viper: Echis ocellatus, Echis pyramidum leakeyi, Echis carinatus sochureki, and Echis coloratus led to identification in each sample of an abundant protein with cytotoxic activity against human non-small cell lung adenocarcinoma A549 cells. The active component in each case was identified by MALDI-TOF mass fingerprinting of tryptic digests as [Ser49]phospholipase A2 (Ser49]PLA2). An isoform of [Ser49]PLA2 containing the single Ala18 -> Val substitution and a partially characterized [Asp49lPLA2 were also present in the E. coloratus venom. LC50 values against A549 cells for the purified [Ser49]PLA2 proteins from the four species are in the range 2.9-8.5 uM. This range is notsignificantly different from the range of LC50 values against human umbilical vein endothelial HUVEC cells (2.5-12.2 uM) indicating that the [Ser49]PLA2 proteins show no differential anti-tumor activity. The LC50 value for |Ser49] PLA2 from E. ocellatusagainst human erythrocytes is >100 uM and the MIC values against Escherichia coli and Staphylococcus aureus are >100 uM. It is suggested that the [Ser49]PLA2 proteins play a major role in producing local tissue necrosis and hemorrhage at the site of envenomation.