Aprotinin is a competitive serine protease inhibitor. Reversibly binds to and blocks the enzymatic active site. Inhibits a range of serine proteases including trypsin, chymotrypsin, kallikrein and plasmin. Inhibits cytopathogenic effect of SARS-CoV-2 and double-stranded RNA formation in SARS-CoV-2-infected cells.

Competitive reversible inhibitor of proteolytic and esterolytic activity. A relatively heat- and acid-stable serine protease inhibitor. Forms a tight complex, blocking the active site of the enzyme. Effective at concentrations equimolar with protease. Inhibits several proteases, including coagulation factors in the prephase of blood clotting, tissue and leukocytic proteinases, chymotrypsin, trypsin (Kd = 5 x 10-14 M), plasmin (Kd = 2.3 x 10-10 M), and kallikrein (Kd = 1 x 10-7 M). Proteases not inhibited by aprotinin include Factor Xa, thrombin, pepsin, papain, and carboxypeptidases A and B. Useful in protein purification and for extending the life of cells in culture by preventing proteolytic damage.

A single-chain polypeptide derived from bovine tissues consisting of 58 amino-acid residues. It is an inhibitor of proteolytic enzymes including CHYMOTRYPSIN; KALLIKREIN; PLASMIN; and TRYPSIN. It is used in the treatment of HEMORRHAGE associated with raised plasma concentrations of plasmin. It is also used to reduce blood loss and transfusion requirements in patients at high risk of major blood loss during and following open heart surgery with EXTRACORPOREAL CIRCULATION.

Aprotinin is a reversible inhibitor of serine proteases such as trypsin (K_i = 0.06 pM), chymotrypsin (K_i = 9.5 nM), and kallikrein (K_i = 0.8 nM). It is a much weaker inhibitor of thrombin (K_i = 0.1-0.8 mM) and trypsinogen (K_i = 2 µM).Aprotinin also competitively inhibits nNOS and iNOS with K_i values of 50 and 78 µM, respectively. Aprotinin is widely used as a protein purification tool to prevent proteases present in tissue samples from degrading the protein of interest.

Proteolytic inhibitor in radioimmunoassays of polypeptide hormones.