12. Activation of Factor X

Activation of Factor X Diagram

  • Cleavage of a peptide bond in the amino end of the heavy chain by either:
    • VIIa-TF
    • IXa-VIIIa

Factor X Downregulation

1. Tissue Factor Pathway Inhibitor (TFPI)
- Xa binds to TFPI to form a complex and inactivate Xa Xi
- TFPI/Xi then inactivates VIIa/TF by forming a quaternary, inactive complex

2. Antithrombin (AT)
- Forms stable complex with Xa, cleared by liver
- Heparin accelerates AT-Xa complex formation