Purification and inhibitory profile of phospholipase A(2) inhibitors from Australian elapid sera

Although the resistance of snakes to their own venom is well known, until n ow no investigators have examined the serum of Australian snakes. Here we d escribe the identification and purification of a range of phospholipase A(2 ) (PLA(2)) inhibitors from the serum of Australian elapids. All PLA(2) inhi bitors were composed of two protein chains, an a-chain and a beta-chain. Th e alpha-chains were approx. 22.5 kDa in size and variably glycosylated, whe reas the beta-chains were approx. 19.8 kDa in size and not glycosylated. Id entification of isoforms of the two subunit chains was significant because three of the six sera examined were from single snake specimens. In additio n, the glycosylation patterns of the alpha-chains were thoroughly investiga ted in these unpooled sera. The functional and structural properties of the purified inhibitors were studied. Uniquely, a snake PLA(2) inhibitor was f ound to inhibit human type II PLA(2) enzyme, which has implications for the treatment of the many diseases in which PLA(2) enzymes have been implicate d. Further, we demonstrate that the inhibitor forms a non-covalent associat ion with a purified PLA(2) enzyme. Finally, the purified PLA(2) inhibitor w as shown to protect in vivo against the lethal affects of a homologous PLA( 2) enzyme, suggesting a role for PLA(2) inhibitors in the treatment of snak e bite victims.