Agkistrodon acutus thrombin-like enzyme (AaTLE)

Thrombin-like serine proteases (TLEs) from the venom of Agkistrodon acutus, such as the well-characterized enzyme Acutin, are specialized enzymes that mimic the proteolytic activity of physiological thrombin (UniProt: P80098). These toxins primarily target fibrinogen, cleaving it to release fibrinopeptide A or B, which initiates the formation of fibrin monomers (PMID: 15621113). Unlike human thrombin, most TLEs from this species do not activate coagulation Factor XIII, meaning the resulting fibrin clots are not cross-linked and remain susceptible to rapid fibrinolysis (PMID: 11566487). This leads to a clinical state of defibrinogenation, where the host's fibrinogen is consumed, resulting in incoagulable blood and a high risk of hemorrhage during envenomation. While these enzymes are significant pathological factors in snakebites, their ability to lower fibrinogen levels has led to research into their use as therapeutic defibrinogenating agents for treating stroke and other thrombotic disorders. They are notably resistant to inhibition by the heparin-antithrombin III complex, distinguishing them from endogenous thrombin in a clinical setting.

Other names

AcutinSharp-nosed pit viper thrombin-like enzymeAgkistrodon acutus serine proteaseSnake venom serine protease

Cleaves fibrinogen into fibrin monomers by specifically releasing fibrinopeptide A or B, leading to the formation of non-cross-linked fibrin and subsequent systemic defibrinogenation (PMID: 15621113).