Protein C inhibitor (PCI) is a serine protease inhibitor and was originally identified as an inhibitor of activated protein C (APC). However, PCI is not specific for APC and also inhibits several proteases involved in coagulation, fibrinolysis, cancer, wound healing, and fertility. The biological function of PCI is unknown due to broad enzyme specificity, its wide tissue distribution, and the lack of a suitable animal model. This review highlights the specific roles of PCI in the areas of hemostasis and thrombosis and fertilization, and it also describes the latest information on the fascinating participation of the protein in intracellular processes, phospholipid binding, and killing of bacteria.
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