protein C / protein S system
Last reviewed 01/2018
Protein C is a vitamin K-dependent protease which complements the anticoagulant activity of antithrombin III by inactivating factors VIII and V. It also stimulates fibrinolysis. It is regulated by protein S on the surface of endothelial cells and requires calcium as a co-factor.
Homozygotes lacking protein C die in the early neonatal period, if not before, from overwhelming coagulation.