Aprotinin inhibits the activity of several proteolytic enzymes such as chymotrypsin，kallikrein，plasmin and trypsin. It is present in blood and in most tissues，with a high concentration in lung，inhibits pro-inflammatory cytokine release and maintains glycoprotein homeostasis. In platelets，Aprotinin reduces glycoprotein loss (e.g.，GpIb，GpIIb/IIIa)，while in granulocytes it prevents the expression of pro-inflammatory adhesive glycoproteins. Aprotinin is a natural proteinase inhibitor polypeptide consisting of fifty-eight amino acids arranged in a single polypeptide chain，cross-linked by three disulfide bridges.
