These studies have shown that jararhagin cleaves fibrinogen preferentially in A-α chains. The hydrolysis of fibrinogen 23 kDa fragment does not interfere in platelet aggregation response, but renders an abnormal fibrin polymerization by thrombin (Kamiguti et al., 1994b). Jararhagin also was able to degrade fibrin in a dose-dependent manner (Baldo et al., 2008). Another effect following interaction between jararhagin and plasma proteins is the enhancement of fibrinolysis due to increase in tissue-type plasminogen activator

activity and inactivation of α2-plasmin inhibitor (Sugiki et al., 1995). According to the authors, these effects occur only because the catalytic activity of jararhagin is unaffected SP600125 nmr by plasma proteinase inhibitors such

as α2-macroglobulin (Kamiguti et al., 1994a). Jararhagin interferes with platelet function by inhibition of collagen- and ristocetin-induced platelet aggregation (Kamiguti et al., 1996a). The inhibition of ristocetin-induced platelet aggregation by jararhagin occurs due to a catalytic effect of the toxin on vWF that hydrolyses the fragment enclosing the AI domain, ligand-site for the GPIb receptor (Kamiguti et al., 1996a). In opposition, jararhagin inhibits collagen-induced platelet aggregation by a multi-factorial mechanism, involving collagen and the α2β1 collagen-receptor, but not interfering with GPVI collagen-receptor BMN 673 concentration (Kamiguti et al., 2000). The cleavage of β1 subunit of the α2β1 integrin by jararhagin was shown, interfering with the stability of α2 subunit that fails to interact with of native collagen via I domain (Kamiguti et al., 1996b). the Moreover, the mechanisms involved in inhibition of platelet aggregation via collagen also include competition between jararhagin and collagen for the binding to α2β1-receptor (De-Luca et al., 1995; Kamiguti et al., 1996a). Specific binding of jararhagin to α2β1 integrin was reported (Moura-da-Silva et al., 2001) as well as its high affinity binding

to the generic triple-helices of type I and type IV collagens (Moura-da-Silva et al., 2008; Tanjoni et al., 2003a). The binding of jararhagin to both α2β1 integrin and collagen would compete with the binding between natural ligand and receptor, interfering with platelet activation. Indeed, in the presence of jararhagin, platelets stimulated with collagen present a reduced phosphorylation of the tyrosine kinase pp72 and FcR gamma-chain Syk phosphorylation (Kamiguti et al., 1997a, 1997b), disrupting the signal transduction induced by collagen. The result of jararhagin action on clotting factors and platelets would corroborate to the unclotable blood, reduction in platelet activity and consequent hemorrhagic lesions that follows B. jararaca envenomings ( Cardoso et al., 1993). Endothelial cells have also been investigated as potential targets for hemorrhagic toxins.