Broad substrate specificity of snake venom fibrinolytic enzymes: possible role in haemorrhage.

We found previously that two fibrinolytic enzymes (jararafibrases I and II) purified from Bothrops jararaca venom displayed a haemorrhagic activity. To elucidate the mechanisms involved and the role of the enzymatic activity in haemorrhage, the enzymatic properties of the purified enzymes were examined. The substrate specificity of the enzymes was determined using type I collagen, type IV collagen, gelatin, laminin and fibronectin as substrates. The enzymes degraded type IV collagen, gelatin, laminin and fibronectin into smaller fragments, but degraded type I collagen only partially in a non-specific manner. The specific activities of jararafibrase I for type IV collagen and gelatin were 172 +/- 5 units/mg protein and 1315 +/- 177 units/mg protein, respectively. The specific activities of jararafibrase II for type IV collagen and gelatin were 9.2 +/- 0.6 units/mg protein and 143 +/- 15 units/mg protein, respectively. It was evident that the enzymes had rather broad substrate specificities and degraded basement membrane components including type IV collagen. The number of type IV collagen units of bacterial collagenase which gave the minimal haemorrhagic dose was 191.4, while the numbers of type IV collagenase units of jararafibrases I and II which gave the minimal haemorrhagic dose were 1.5 and 0.25, respectively. It is suggested that the broad substrate specificity of the enzymes is essential for inducing haemorrhage with a single enzyme.