Characterisation of a purified phospholipase A2 from the venom of the Papuan black snake (Pseudechis papuanus).

A neutral phospholipase A2 (PLA2) was separated from Pseudechis papuanus venom by a two-stage FPLC procedure of cation exhange and phenyl-Superose chromatography. It had a molecular mass of 15 kDa and a lower LD50 value than a co-separated haemorrhagic fraction, indicating a higher lethal potency. In vitro tests confirmed the powerful inhibition of platelet aggregation by the PLA2 and strong anticoagulant activity initially observed with whole venom. Ultrastructural studies showed that platelets lost their discoid shape and developed membranous projections with a general decrease in electron-density of the cytosol and disruption of the microfilaments following incubation with the enzyme. Amino acid sequence analysis of the N-terminus and some internal peptides demonstrated a high degree of homology with PLA2s from other Pseudechis venoms. Our results indicate that this fraction is the main agent responsible for the haemostatic disorders in envenomed patients.