Purification and characterization of lebetase, a fibrinolytic enzyme from Vipera lebetina (snake) venom.

An anticoagulant proteinase, lebetase, was isolated from the venom of Vipera lebetina by gel filtration and anion-exchange chromatography. The proteinase consists of a single polypeptide chain with a molecular weight of 23,700. Amino acid analysis indicates that lebetase contains 214 residues. It consists of several isoforms in the pH range 4.6-5.4, all having fibrinolytic activity. Lebetase hydrolyzes casein, fibrinogen and fibrin, and oxidized insulin B-chain in the positions Ala14-Leu15 and Tyr16-Leu17. Its fibrinolytic activity is inhibited by EDTA and lost upon heating at 70 degrees C for 10 min. The enzyme readily hydrolyzes the A alpha-chain and more slowly the B beta-chain of fibrinogen. In fibrin, the same chains are attacked. Thus, the enzyme is an A alpha, B beta-fibrinogenase. The fibrinolytic activity of lebetase is direct, without any plasminogen activation. E280 1% is 13.0 for lebetase. The enzyme showed low hemorrhagic activity.