What is a tissue factor pathway inhibitor?

Updated: Feb 07, 2020
  • Author: Bishnu Prasad Devkota, MD, MHI, FRCS(Edin), FRCS(Glasg), FACP; Chief Editor: Eric B Staros, MD  more...
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Answer

Tissue factor pathway inhibitor

Depending on the degree of proteolysis of the carboxy-terminal region, TFPI, a single-chain polypeptide, has an Mr of 34,000-40,000. Unlike other coagulation protease inhibitors, TFPI has inhibitory sites for factor Xa and for the factor VIIa/tissue factor (TF) complex, and it cannot inhibit the factor VIIa/TF complex without being bound to factor Xa. [2, 3]

Endothelial cells are the primary site of plasma TFPI synthesis. [4] Most circulating TFPI is bound to lipoproteins, but on the surface of endothelial cells, a second pool of TFPI is bound to heparan sulfates. When heparin is administered, the endothelial cell–bound TFPI is released and the plasma level rises severalfold. [5]

TFPI exists in the plasma at only about 2.5 nM, while antithrombin occurs at about 2 µmol. However, TFPI and antithrombin have a similar rate of reaction with factor Xa in plasma. Therefore, TFPI makes a significant contribution to factor Xa inhibition in vivo. [6] The human TFPI gene is found on chromosome 2.


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