PCI is a non-specific serpin that inhibits several proteases of the coagulation and fibrinolytic
systems as well as plasmaand tissue kallikreins and the sperm protease acrosin. The
precise physiological role of PCI has not been defined yet. Heparin stimulates most
PCI/protease reactions, but interferes with the tissue kallikrein/PCI-interaction. Thereby
heparin not only regulates PCI-activity but also its specificity in systems containing two or
more of its target proteases. This effect is not restricted to heparin, but is also seen with other …