Thrombomoduin and Protein C





Protein C

  • Activated by thrombomodulin-thrombin complex

  • Activated protein C (APC) forms a complex with protein S

  • The APC/ProS complex inactivates

    • Factor Va
    • Factor VIIIa
    • Plasminogen activator inhibitor 1

NB:

  • Inactivation of plasminogen activator inhibitor 1 ultimately promote fibrinolysis (it's a triple negative)

  • APC/ProS complex is more efficient inactivator (of factor Va)
    ... when the complex is on endothelial cell surface than on platelet surface

  • Both protein C and protein S are vitamin K dependent plasma glycoproteins

Thrombomodulin

All endothelial cells (except those in cerebral microcirculations) produce thrombomodulin

Thrombomodulin binds to thrombin
→ Thrombomodulin-thrombin complex → Activates protein C

Expression of thrombomodulin is 100 times higher in capillary endothelium, compared to endothelium in the major vessels