Pseudonaja prothrombin activator (PPA)

Shared coagulotoxins from Pseudonaja venoms, primarily represented by the Pseutarin C-like prothrombin activators, are potent enzymatic complexes that mimic the human prothrombinase complex. These toxins are composed of two subunits structurally and functionally analogous to mammalian blood coagulation Factor Xa and Factor Va. Their primary biological function is the rapid and calcium-independent conversion of prothrombin into thrombin, which leads to massive fibrinogen consumption and the formation of microthrombi. In the context of human envenomation, this activity results in venom-induced consumption coagulopathy (VICC), a life-threatening condition characterized by non-clottable blood and a high risk of internal bleeding. These coagulotoxins are the primary therapeutic targets for brown snake antivenoms, which neutralize the enzymatic activity to restore normal hemostasis. Beyond toxicology, these molecules serve as significant models for studying the assembly and regulation of the mammalian coagulation cascade.

Other names

Pseutarin CPseudonaja textilis prothrombin activatorGroup C prothrombin activatorSnake venom prothrombinase complexFactor Xa-Factor Va-like complex

Antivenoms contain specific antibodies (F(ab')2 or IgG) that bind to the prothrombin activator complex, neutralizing its enzymatic activity and preventing the conversion of prothrombin to thrombin.