The Mechanism of Blood Anticoagulation by Leech Hementin
Anticoagulation of blood by the leech Hirudo medicinalis is accomplished by hirudin, a potent inhibitor of thrombin. The giant South American leech Haementeria ghilianii also renders blood incoagulable in order to feed and digest the meal. However, the mechanism of blood anticoagulation by the latter leech is different from the former. The anticoagulant, called hementin, is present in both the anterior and posterior salivary glands. It is a metalloproteinase that specifically cleaves fibrinogen rendering it incoagulable by thrombin. The mechanism of degradation by this enzyme involves preferential hydrolysis of three peptide bonds in the coiledcoil connector, resulting in destruction of bivalent function of the fibrinogen molecule. Since the other coagulation factors in human blood are unaffected by hementin, the mechanism of action of this anticoagulant is selectively focused on fibrinogen.
KeywordsSalivary Gland Human Fibrinogen High Molecular Weight Kininogen Salivary Gland Extract Blood Anticoagulation
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