Draculin
Draculin is a novel protein isolated from the saliva of vampire bats (Desmodus rotundus), characterized by its anticoagulant activity for mammalian blood[1][2]. This protein has been found to inhibit both Factors IX and X of the blood coagulation cascade, making it distinct from known anticoagulants[1]. Draculin is a single-chain polypeptide protein composed of 708 amino acids, with a molecular weight of approximately 88.5 kDa when reduced and 83 kDa when non-reduced[2]. It functions as a noncompetitive, tight-binding inhibitor of activated factor X (FXa), forming equimolar complexes with FXa[2][3]. The inhibition upon contact with the blood of the victim is immediate, and Draculin does not act on thrombin, trypsin, or chymotrypsin, nor does it express fibrinolytic activity[2][3]. The biological activity of Draculin is highly dependent on glycosylation of the native protein and can be severely affected by the salivation pattern of the animals[2].
Draculin has been substantially purified using methods such as dialysis, hydroxyapatite chromatography, and ultrafiltration[1]. It is characterized as having an anticoagulant activity that is stable for at least seven days at room temperature and stable after repeated freezing and thawing[1]. The calculated molecular weight of Draculin is approximately 75 kDa, with differences between the apparent molecular weights estimated using different methods reflecting the relative sensitivities or limitations of the methods themselves, whether the Draculin is glycosylated or not, and/or other post-translational processing of native Draculin, or a combination of these factors[1].
Research has shown that Draculin is a tight-binding, noncompetitive inhibitor of activated factor X, with a kinetic mechanism of action established[3]. The formation of the Draculin-FXa complex can be explained by a two-step mechanism, with the first reversible step characterized by specific rate constants and the second irreversible step being concentration-independent[3]. The dissociation constant is determined as the ratio of the rate constants, and the Lineweaver-Burk plot shows a noncompetitive behavior[3].
Draculin has been considered for its potential therapeutic applications, particularly in the treatment of thrombosis[4]. A national study has been conducted to explore the use of bat-inspired drugs, including Draculin, in extending the treatment window for stroke patients[5]. The study aims to determine if a compound extracted from vampire bat saliva can help patients survive a stroke by dissolving blood clots more effectively than current treatments[5].
Citations:
[1] https://patents.google.com/patent/WO1995005836A1/en
[2] https://en.wikipedia.org/wiki/Draculin
[3] https://pubmed.ncbi.nlm.nih.gov/10556567/
[4] https://synapse.patsnap.com/drug/f067b8529a2d454b8cd01fb9c05516a3
[5] https://www.zdnet.com/article/vampire-bat-saliva-breaks-up-blood-clots/