The blood coagulation cascade (Fig.1) is a series of reactions, in which a zymogen (inactive enzyme precursor) of a serine protease and its glycoprotein co-factor are activated and then catalyze the next reaction in the cascade, ultimately resulting in cross-linked fibrin.
The coagulation factors are principally serine proteases, which act by cleaving downstream proteins. There are some exceptions. For example, FVIII and FV are non-enzymatic oxidases, and Factor XIII is a transglutaminase. The coagulation factors circulate as inactive zymogens. The coagulation cascade is classically divided into three pathways. The tissue factor and contact activation pathways both activate the final common pathway of factor X, thrombin and fibrin.
Figure 1: Blood coagulation cascade (Image from
Wikimedia / licensed under Creative Commons).
Venom blood coagulation cascade activating toxins activate components of the blood coagulation cascade and cause an imbalance in hemostasis.
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