Table 1. Anticoagulant proteins from snake venom.

Protein		Mechanism of action	Remarks
Enzymatic anticoagulant proteins
1. Phospholipase A2 enzymes	Strongly anticoagulant	Inhibits activation of FX to FXa by extrinsic tenase complex	By both enzymatic and non-enzymatic mechanisms; target protein not known
		Inhibits activation of prothrombin to thrombin by prothrombinase complex	By non-enzymatic mechanism; binds to FXa and interferes in the prothrombinase complex formation
	Weakly anticoagulant	Inhibits activation of FX to FXa by extrinsic tenase complex	By non-enzymatic mechanism through hydrolysis of phospholipids
2. Metalloproteinases (α-fibrinogenase)		Weaker soft clot formation due to physical destruction of fibrinogen	By cleaving Aα-chain of fibrinogen
3. Serine proteinases	Protein C activators	Inactivation of cofactors FVa and FVIIIa degradation	Directly activate protein C
	Thrombin-like enzymes	Deplete fibrinogen in the plasma	Releases either fibrinopeptide A or B; fibrin clots are removed leading to depletion of fibrinogen content
	Fibrinogenases	Physical destruction of fibrinogen	Mechanism not known
4. L-Amino acid oxidase		Inhibits FIX activity	Mechanism not known
Non-enzymatic anticoagulant proteins
1. C-type lectin related proteins	FX and FIX binding proteins	Inhibit the formation of coagulation complexes	Bind to the Gla domain of FIX and FX, and interfere in their binding to phospholipids
	Bothrojaracin, bothroalternin	Inhibit the activity of thrombin	Bind to α-thrombin at both exosite-1 and exosite-2
2. Three-finger toxin	Cardiotoxins from Naja nigricollis crawshawii venom	Act on the extrinsic pathway of the clotting cascade	Mechanism not known
	Hemextin A and hemextin AB complex from Hemachatus haemachatus venom	Prevents clot initiation by inhibiting extrinsic tenase activity	Specifically binds to FVIIa