Isolation and characterization of an endogenous inhibitor of phospholipase A2 from Indian cobra (Naja naja naja) venom.

A PLA2-inhibitor has been purified from Indian cobra (Naja naja naja) venom by the combination of ion-exchange and gel-filtration chromatography. The inhibitor, NN-I3 was a peptide with mol.wt 6500 and has a fluorescence emission maxima ca 340 nm. NN-I3 specifically inhibited the enzyme activity of the three acidic PLA2 from the same venom. The inhibition of NN-I2d-PLA2 and NN-I2c-PLA2 by NN-I3 was of mixed type and NN-I2c-PLA2 was of uncompetitive type. Neither the inhibitor nor the individual mixtures of acidic PLA2 with the inhibitor (1:1 w/w or 1:2 mol:mol) were lethal to mice when injected intraperitoneally in doses up to 10 mg kg(-1) body weight.