EFFECTS OF PALLAS-VIPER (AGKISTRODON HALYS PALLAS) VENOM ON BLOOD-COAGULATION AND CHARACTERIZATION OF A PROTHROMBIN ACTIVATOR

The action of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation was examined in vitro and a strong anticoagulant effect wa s observed. This action was abolished after treatment with a specific inhibitor of phospholipase A(2) activity (p-bromophenacyl bromide), re vealing a procoagulant action in low concentrations of treated venom ( around 1 mu g/ml). The effect of the venom an haemostasis was further characterized by measuring its ability to activate purified blood coag ulation factors. It is concluded that A. halys pallas venom contains p rothrombin activation activity. A prothrombin activator (aharin) was p urified from the venom by Sephadex G-75 gel filtration and ion-exchang e chromatography on a Mono-Q column. It consisted of a single polypept ide chain, with a mol. wt of 63,000. Purified aharin possessed no amid olytic activity on chromogenic substrates. It did not act on other blo od coagulation factors, such as factor X and plasminogen, nor did it c leave or clot purified fibrinogen. The prothrombin activation activity of aharin was readily inhibited by ethylenediamine tetracetic acid (a metal chelator), but specific serine protease inhibitors such as diis opropyl fluorophosphate and phenylmethanesulfonyl fluoride had no effe ct on it. These observations suggest that, like those prothrombin acti vators from Echis carinatus and Bothrops atrox venoms, the prothrombin activator from A. halys pallas venom is a metalloproteinase. (C) 1998 Elsevier Science Ltd. All rights reserved.