Isolation of an acidic phospholipase A2 from the venom of Agkistrodon acutus (five pace snake) and its effect on platelet aggregation

Abstract Rui-Hong Chen and Yuan-Chung Chen . Isolation of an acidic phospholipase A 2 from the venom of Agkistrodon acutus (five pace snake) and its effect on platelet aggregation. Toxicon 27, 675–682, 1989.—A phospholipase A 2 from the venom of the snake Agkistrodon acutus was purified by immunoaffinity chromatography and fast protein liquid chromatography (FPLC) as a single band by PAGE and SDS-PAGE. The estimated mol.wt was 16,400 by SDS-PAGE and 16,900 by gel filtration and the isoelectric point was 4.9. The ten N -terminal amino acid residues are homologous to those of the acidic phospholipases A 2 from other crotalid venoms. The purified enzyme showed a potent inhibitory effect on platelet aggregation induced by ADP, collagen and sodium arachidonate in human platelet-rich plasma. The platelet aggregation by these inducers was completely suppressed when the concentration of the venom phospholipase A 2 was 10–100 μg/ml. However, at 20 μg/ml, platelet aggregation could be elicited in washed human platelet suspension. Aspirin (28 μg/ml), an inhibitor of cyclooxygenase, inhibited the aggregating effect of the phospholipase A 2 . It is proposed that the stimulatory mechanism of the phospholipase A 2 might be due to the liberation of arachidonic acid from phospholipids in the membrane of platelets and the formation of thromboxane A 2 .