CHARACTERIZATION OF A PURIFIED PHOSPHOLIPASE A(2) FROM THE VENOM OF THE PAPUAN BLACK SNAKE (PSEUDECHIS-PAPUANUS)

A neutral phospholipase A(2) (PLA(2)) was separated from Pseudechis pa puanus venom by a two-stage FPLC procedure of cation exchange and phen yl-Superose chromatography. It had a molecular mass of 15 kDa and a lo wer LD(50) value than a co-separated haemorrhagic fraction, indicating a higher lethal potency. In vitro tests confirmed the powerful inhibi tion of platelet aggregation by the PLA(2) and strong anticoagulant ac tivity initially observed with whole venom. Ultrastructural studies sh owed 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 en zyme. Amino acid sequence analysis of the N-terminus and some internal peptides demonstrated a high degree of homology with PLA(2)s from oth er Pseudechis venoms. Our results indicate that this fraction is the m ain agent responsible for the haemostatic disorders in envenomed patie nts.