Vampire bats are sanguivorous or blood-eating bats. When they bite their victim, a protein in their saliva acts as an anticoagulant, which keeps their victim’s blood flowing while they feed. This anticoagulant contains the protein desmoteplase or DSPA, which was given the nickname Draculin. During the blood clotting process, DSPA inhibits Factor X, which is an enzyme involved in the coagulation pathway.
“There is a protein in the vampire bat’s saliva that might one day benefit stroke sufferers, especially those who ignore their symptoms for several hours before calling 911 or going to the hospital…This enzyme–called desmoteplase, or DSPA–is what interests stroke experts. For more than eight years, researchers have studied it to see whether it can dissolve blood clots that starve the brain of oxygen during a stroke. ‘When you inject (the enzyme) intravenously in a human it can also keep the blood flowing,’ Torbey said.”
“Activation of Factor X is a common point between the intrinsic and extrinsic pathway of blood coagulation . Activated factor X (FXa) is the sole enzyme that catalyzes the conversion of prothrombin into thrombin, the key enzyme in the coagulation cascade; therefore inhibitors of this step are of considerable mechanistic and pharmacological interest. In addition to the two known physiological inhibitors of this serine protease, antithrombin III (AT-III) and the tissue factor pathway inhibitor (TFPI), several low molecular mass naturally occurring polypeptides inhibitors have been described, such as Antistasin, a 119-residue protein isolated from the mexican leech Haementeria offcinalis [2,3]; the tick anticoagulant peptide (TAP) , a 60-amino acid protein derived from the tick Ornithodoros moubata; Ecotin, a periplasmic protein found in Escherichia coli [5-7]; and the Ancylostoma caninum anticoagulant peptide (AcAP) . These peptides behave as reversible, slow tight-binding inhibitors of FXa, where Antistasin and Ecotin are slowly cleaved by FXa, while TAP is not affected by the protease. Recently, we described a new natural FXa inhibitor, isolated from the saliva of the vampire bat Desmodus rotundus, which was named Draculin. Draculin is a 88.5 kDa glycoprotein which selectively inhibits both FXa and activated factor IX (FIXa) . Furthermore, the anticoagulant activity of Draculin is highly dependent on the proper glycosylation of the polypeptide backbone . The results described in this paper indicate that, in contrast to other natural FXa inhibitors, Draculin behaves as a noncompetitive, tight-binding inhibitor of FXa.” (Fernandez et al. 1999:135-136)