title: Tick anticoagulant peptide: kinetic analysis of the recombinant inhibitor with blood coagulation factor Xa.
abstract: Tick anticoagulant peptide (TAP) is a 60 amino acid protein which is a highly specific inhibitor of human blood coagulation factor Xa (fXa) isolated from the tick Ornithodoros moubata [Waxman, L., Smith, D. E., Arcuri, K. E., & Vlasuk, G. P. (1990) Science 248, 593-596]. Due to the limited quantities of native TAP, a recombinant version of TAP produced in Saccharomyces cerevisiae was used for a detailed kinetic analysis of the inhibition interaction with human fXa. rTAP was determined to be a reversible, slow, tight-binding inhibitor of fXa, displaying a competitive type of inhibition. The binding of rTAP to fXa is stoichiometric with a dissociation constant of (1.8 +/- 0.02) x 10(-10) M, a calculated association rate constant of (2.85 +/- 0.07) x 10(6) M-1 s-1, and a dissociation rate constant of (0.554 +/- 0.178) x 10(-3) s-1. Binding studies show that 35S-rTAP binds only to fXa and not to DFP-treated fXa or zymogen factor X, which suggests the active site of fXa is required for rTAP inhibition. That rTAP is a unique serine proteinase inhibitor is suggested both by its high specificity for its target enzyme, fXa, and also by its unique structure.
authors: Biological Chemistry Department, Merck Sharp & Dohme Research Laboratories, West Point, Pennsylvania 19486.
authors: S P
authors: SP
authors: Jordan
authors: L
authors: L
authors: Waxman
authors: D E
authors: DE
authors: Smith
authors: G P
authors: GP
authors: Vlasuk
mesh_terms: D000818:Animals; D060829:Arthropod Proteins; D015951:Factor Xa / Q000378:metabolism*; D065427:Factor Xa Inhibitors; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D009994:Osmolar Concentration; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013987:Ticks
chemical_list: D060829:Arthropod Proteins; D065427:Factor Xa Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011994:Recombinant Proteins; C063967:tick anticoagulant peptide; D015951:Factor Xa