Proteases from Vipera lebetina venom affecting coagulation and fibrinolysis

Abstract

Our studies of the venom from the Levantine viper Vipera lebetina have demonstrated the existence of both coagulants and anticoagulants in the same venom. We showed that V. lebetina venom contains: (1) proteases that degrade fibrinogen, but not fibrin; (2) fibrinolytic enzyme (lebetase); (3) factor X activator (VLFXA); (4) factor V activator (VLFVA). Fibrinolytic enzyme and VLFXA are metalloproteases; the other studied enzymes are serine proteases. α-Fibrinogenase has no homolog among known serine proteases. β-Fibrinogenase is a typical thermostable arginine esterase that hydrolyzes esters and amides of arginine and attacks the β-chain of fibrinogen. Lebetase is a direct-acting fibrinolytic zinc metalloendopeptidase related in amino acid sequence to reprolysins. We used the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technique for the recovery and identification of peptides released by protease hydrolysis and for the detection of human factor X cleavage products after VLFXA hydrolysis. VLFXA cleaves the Arg52-Ile53 bond in the heavy chain of human factor X and the Arg226-Val227 bond in human factor IX precursor; VLFVA cleaves Arg1545-Ser1546 in factor V. Copyright © 2002 S. Karger AG, Basel.