Anticoagulant and Fibrinolytic Properties of Salivary Proteins from the Leech Haementeria ghilianii

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Abstract
The salivary glands of the blood-sucking leech Haementeria ghilianii contain an anticoagulant that not only inhibits the clotting of human and bovine plasma, but also dissolves previously formed fibrin clots. This anticoagulant activity is attributable to an enzyme, for which the name hementin is proposed. Hementin catalyzes the proteolytic degradation of fibrinogen and fibrin, even in the presence of the inhibitors of proteases occurring in human plasma. The enzyme has the same affinity for human fibrinogen and fibrin. In human fibrinogen cleaves the Act chain initially and then the γ chain to yield characteristic fragments of high molecular weight that are different from the fragments resulting from the digestion of fibrinogen by plasmin. The salivary extracts do not contain any appreciable amounts of an activator of human plasminogen or an inhibitor of human or bovine thrombin. Thus, H. ghilianii prevents coagulation of its host blood through a fibrinogenolytic mechanism that is entirely different from that of hirudin, a thrombin-inactivating polypeptide present in the saliva of another leech, Hirudo medicinalis.