<p>Leeches, such as <taxon tax_id="6421">Hirudo medicinalis</taxon> (Medicinal leech), produce a variety of antihaemostatic proteins that act as proteinase inhibitors. These inhibitors are used to aid the leech in feeding upon its host by blocking blood coagulation [<cite idref="PUB00014230"/>, <cite idref="PUB00014233"/>]. Examples of these proteins include hirustasin (inhibitor of tissue kallikrein, trypsin, alpha-chymotrypsin, and granulocyte cathepsin G) [<cite idref="PUB00014232"/>], bdellastasin (inhibitor of trypsin, plasmin, and acrosin) [<cite idref="PUB00014231"/>], factor Xa inhibitor antistasin (inhibitor of blood coagulation factor Xa) [<cite idref="PUB00010320"/>], hirudin (thrombin inhibitor), decorsin (inhibitor of platelet aggregation) [<cite idref="PUB00014234"/>] and haemadin (thrombin inhibitor) [<cite idref="PUB00014235"/>].</p>