Purification and characterization of an anticoagulant phospholipase A2 from Indian monocled cobra (Naja kaouthia) venom

Abstract

An anticoagulant, non-toxic phospholipase A2 was isolated from the venom of Indian monocled cobra (Naja kaouthia) by a combination of ion-exchange chromatography on CM-Sephadex C-50 and gel filtration on Sephadex G-50. This purified protein named NK-PLA2-I, had a subunit molecular mass of 13.6 kDa and migrated as a dimer under non-reduced condition in SDS-PAGE. NK-PLA2-I was a highly thermostable protein requiring basic pH optima for its catalytic activity and showed preferential hydrolysis of phosphotidylcholine. This protein exhibited higher anticoagulant, indirect hemolysis, liver and heart tissue damaging activity but exerted less toxicity, direct hemolysis, edema and lung tissue damaging activity as compared to whole venom. Treatment of NK-PLA2-I with ρ-BPB, TPCK, PMSF, antivenom and heating had almost equal effect on PLA2, and other pharmacological properties except in vitro tissue damaging activity. Current investigation provides a fairly good indication that NK-PLA2-I induces various pharmacological effects by mechanisms, which are either dependent or independent of its catalytic activity.