A potent platelet aggregation inhibitor purified from Agkistrodon halys (mamushi) snake venom.

By means of gel filtration on Sephadex G-75, DEAE-Sephadex A-50 column chromatography and three gel filtrations on Sephadex G-75, a potent platelet aggregation inhibitor was purified from Agkistrodon halys snake venom and shown to be a single peptide chain, as judged by SDS-polyacrylamide gel electrophoresis. The purified platelet aggregation inhibitor was an acidic protein with a molecular weight of 14,000 and possessed phospholipase A2 activity. Its inhibitory activity on platelet aggregation was heat stable (at 96 degrees C, 30 min) in an acidic medium (pH 5.5), while its phospholipase A enzymatic activity was heat labile under the same conditions. Its inhibitory activity on platelet aggregation induced by thrombin, sodium arachidonate, collagen or ionophore A-23187 was non-competitive and dose-dependent with a similar ID50 (approximately 11 micrograms/ml). It exerted its inhibitory action without pre-incubation with platelet suspension, however, its inhibitory effect could be moderately increased after longer incubation (30 min).