Probably essential to support the feeding habits of this exclusively haematophagous animal. Potent thrombolytic agent. Specific cleavage of Arg-|-Val bond in plasminogen to form plasmin. Activity toward plasminogen is stimulated in the presence of fibrin I. Monomer. The fibronectin type-I domain mediates binding to fibrin, and the kringle domain apparently mediates fibrin-induced stimulation of activity. Belongs to the peptidase S1 family.