A serine protease inhibitor which is reactive against trypsin, chymotrypsin, plasmatic and glandular kininogenases, plasmin, kallkrein, urokinase, clotting factor XIIa, protein C, proteinases of the complement system, and leukocyte and tissue proteinases.

• Serine protease inhibitor
• CAS: 9087-70-1
• Relatively stable
• Off-White Powder
• Store at +4 °C.
• Extinction Coefficient: 8.3 (water)(280 nm)
• Isoelectric Point: 10.5 10 (Lit.)
• pH: 5.0 - 7.0 (1% aq soln)
• Bovine Lung source
• Specific Activity: ~6000 KIU/mg
• Surface Area: Equimolar with protease (1-2 ug/mL).
• KIU: One KIU (Kallikrein Inactivating Unit) is identical to the quantity of protease inhibitor that has the ability to inhibit 2 Kallikrein units by 50% under optimal conditions.

Aprotinin is relatively stable to high temperature, acids, alkali, organic solvents and proteolytic digestion (only thermolysin has been found capable of degrading aprotinin after heating to 60-80 °C)

Small amounts of aprotinin can be added to tubes of drawn blood to enable laboratory measurement of rapidly degraded proteins such as glucagon. Aprotinin can be labelled with fluorescein isothiocyanate. The conjugate retains its antiproteolytic and carbohydrate-binding properties and has been used as a fluorescent histochemical reagent for staining glycoconjugates (mucosubstances) that are rich in uronic or sialic acids. In cell biology aprotinin is used as an enzyme inhibitor to prevent protein degradation during lysis or homogenization of cells and tissues.

Synonyms include Pancreatic Basic Trypsin Inhibitor polypeptide; Antagosan; Antikrein; Trasylol; Zymofren; Antagosan; Anikrein; Antilysin(e); BPTI; Bayer A 128; Kallikrein-trypsin inactivator; Fosten; Iniprol; Kunitz protease inhibitor; Onquinin; Repulson; RP-9921; Ryker 52G; Triazinin; Zymofren

The Cyc-Cys disulfide bridge is readily split by reducing agents like b-mercaptoethanol. Aprotinin is found in bovine lymph nodes, lung, parotid gland, spleen, liver, pancreas, seminal vesicles, thyroid gland, kidney, mucous membranes of the trachea and esophagus, ovaries, heart, posterior pituitary and cartilage. It does not inhibit thrombin. Aprotinin works by blocking the active sites of enzymes. Binding is reversible with most aprotinin-protease complexes dissociating at pH > 10 or < 3.