Hematophagy and inhibition of the extrinsic and intrinsic tenase complexes

The coagulation cascade involves the regulated sequence of proteolytic activation of a series of zymogens culminating in conversion of fibrinogen to fibrin and clot formation. These reactions are mainly performed by enzymatic complexes comprised of a serine protease, a protein cofactor and membranes containing anionic phospholipids. A number of specific coagulation inhibitors from exogenous sources have been identified from salivary glands of blood-sucking arthropods and herein named sialogenins (from the Greek sialo, saliva; gen, origin, source; and ins for proteins) with anticlotting activity. Anti-clotting sialogenins target components of the extrinsic (e.g. ixolaris, penthalaris, NAPc2) or intrinsic Xase (e.g. nitrophorin 2, nitrophorin 7) complexes resulting in inhibition of the initiation, propagation or consolidation steps of blood coagulation cascade. In addition, these molecules act in a redundant and synergistic manner in order to keep hemostatic tonus as low as possible so as to facilitate blood-feeding. These molecules may also attenuate inflammatory events associated with vascular injury. Finally, anti-clotting sialogenins have potential therapeutic applications and are valuable tools in pharmacology and cell biology.