Purification and inhibitory profile of phospholipase A2 inhibitors from Australian elapid sera

Abstract

Although the resistance of snakes to their own venom is well known, until now no investigators have examined the serum of Australian snakes. Here we describe the identification and purification of a range of phospholipase A2 (PLA2) inhibitors from the serum of Australian elapids. All PLA2 inhibitors were composed of two protein chains, an α-chain and a β-chain. The α-chains were approx. 22.5 kDa in size and variably glycosylated, whereas the β-chains were approx. 19.8 kDa in size and not glycosylated. Identification of isoforms of the two subunit chains was significant because three of the six sera examined were from single snake specimens. In addition, the glycosylation patterns of the α-chains were thoroughly investigated in these unpooled sera. The functional and structural properties of the purified inhibitors were studied. Uniquely, a snake PLA2 inhibitor was found to inhibit human type II PLA2 enzyme, which has implications for the treatment of the many diseases in which PLA2 enzymes have been implicated. Further, we demonstrate that the inhibitor forms a non-covalent association with a purified PLA2 enzyme. Finally, the purified PLA2 inhibitor was shown to protect in vivo against the lethal affects of a homologous PLA2 enzyme, suggesting a role for PLA2 inhibitors in the treatment of snake bite victims.