SERPINA5 (also called Protein C Inhibitor,PCI ) is a serpin type of serine protease inhibitor that is found in many tissues and fluids in human,including blood plasma,seminal plasma and urine. PCI found in blood originates from the liver and is capable of inhibiting several serine proteases involved in the regulation of coagulation and fibrinolysis,including activated protein C,thrombin,factor Xa,various kallikreins and plasminogen activators. PCI has been found to have antimicrobial and antitumor properties and thus appears to be a multi-functional protein.