Article

Tick Anticoagulant Peptide (TAP) Is a Novel Inhibitor of Blood Coagulation Factor Xa

Lloyd WaxmanBiological Chemistry Department, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486Donna SmithBiological Chemistry Department, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486Karen E. ArcuriBiological Chemistry Department, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486Geroeg P. VlasukBiological Chemistry Department, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486

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Abstract

A low molecular weight serine protease inhibitor (TAP) was purified from extracts of the soft tick, Ornithodoros moubata. The peptide is a slow, tight-binding inhibitor, specific for factor Xa (Ki = 0.588 +/- 0.054 nM). The inhibitor also acts as an anticoagulant in several human plasma clotting assays in vitro. Its amino acid sequence (60 residues) has limited homology to the Kunitz-type inhibitors. However, unlike other inhibitors of this class, TAP inhibits only factor Xa. It had no effect at a 300-fold molar excess on factor VIIa, kallikrein, trypsin, chymotrypsin, thrombin, urokinase, plasmin, tissue plasminogen activator, elastase, or Staphylococcus aureus V8 protease. TAP's specificity and size suggest that it may have therapeutic value as an anticoagulant.

Identifiers

DOI: 10.1126/science.2333510

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Cited by 20 references

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