Purification and properties of several phospholipases A2 from the venom of Australian king brown snake (Pseudechis australis)

Abstract Thirteen isoenzymes of phospholipases A 2 were purified from the venom of Australian king brown snake, Pseudechis australis . They (except phospholipase A 2 Pa-9C) showed normal properties of snake venom phospholipases A 2 ; the apparent mol. wts were about 13,000, the optimum pH values were around 8, calcium ion was indispensable for the enzymatic activity and the optimum calcium ion concentrations were more than 5 mM. Phospholipase A 2 Pa-9C had a lag period at the initial stage of the enzymatic reaction. The enzymatic activities determined by the titration method using 1,2-dipalmitoylglycerophosphocholine as a substrate at 37°C were 10,500 units/mg for Pa-1G and 75 units/mg for Pa-13. The lethal activities measured by i.v. injections in mice were 0.09 μg/g body wt for Pa-5 and 6.8 μg/g body wt for Pa-13. The lethal activity correlates with the enzymatic activity (correlation coefficient of 0.92), and both activities showed no relationship to the basicity of the enzyme. Pa-1G is the first acidic phospholipase A 2 (pI = 6.4) with high neurotoxicity (0.13 μg/g body wt).