Aprotinin

Trypsin inhibitor, pancreas type from bovine lung. It is known as Pancreatic trypsin inhibitor (BPTI). Aprotinin, also known as pancreatic trypsin inhibitor and trypsin-kallikrein inhibitor, is found to be expressed in lungs, spleen, liver, and pancreas. It is also found to be present in the free form in calf serum.

Aprotinin inhibits serine proteases. It inhibits kallikrein, the protease that releases hypotensive peptides such as kallidin and bradykinin (human plasma kallikrein: K_i = 3 ×10^-8 M at pH 8.0, porcine pancreas kallikrein: K_i = 1 × 10^-9 M at pH 8.0), trypsin (K_i = 2.8 × 10^-11 M at pH 7.8, K_i = 2.6 × 10^-9 M at pH 4.0, non-competetive), trypsinogen, chymotrypsin (K_i = 9 × 10^-9 M at pH 8.0), bacterial fibrinolysin, and plasmin (K_i = 1 nM at pH 7.3).
Cathepsin G, acrosin, human leukocyte elastase, and human urokinase are weakly inhibited. Factor Xa, thrombin, subtilisin, papain, pepsin, angiotensin-converting enzyme (ACE), carboxypeptidase A and B, other metalloproteases, and thiolproteases are not inhibited.

Aprotinin is used for the protection of proteins and enzymes during isolation/purification. The inhibition of protease activity increases the lifetime of cells in cell and tissue culture studies.

• Further applications: Purification of urokinase, trypsin, and chymotrypsin on immobilized aprotinin
• Quantification of kallikrein activity in mixtures of esterases and proteases
• Controlled degradation of substrates by avoiding nonspecific proteolysis in clinical chemical tests
• Aprotinin as a model protein in protein-folding studies
• Molecular weight marker in SDS-polyacrylamide gel electrophoresis

Monomeric peptide of 58 amino acids held in conformation by three disulfide bonds.

One inhibitor unit (IU) is defined as the amount of aprotinin that completely inhibits 1 U trypsin in < 10 minutes at pH 6. (Trypsin activity determined at +25 °C, pH 8.0, BAEE as substrate).
One inhibitor unit (IU) (+25 °C, BAEE as substrate) corresponds to about 2.8 inhibitor units (+25 °C, Chromozym TRY as substrate).
One inhibitor unit (IU) (+25 °C, BAEE as substrate) corresponds to about 26 kallikrein inhibitor units (KIU) (+25 °C).
One inhibitor unit (IU) (+25 °C, BAEE as substrate) corresponds to about 0.067 inhibitor units (+25 °C; Bz-D,L-Arg-4-Na as substrate, trypsin determination at pH 7.8).
One kallikrein inhibitor unit = 0.17 μg crystalline aprotinin.

Working concentration: 0.06 to 2 μg/ml (0.01 - 0.3 μM)
Working solution: Soluble in water (10 mg/ml) or aqueous buffer solution (e.g., 0.1 M Tris, pH 8.0).
Note: To avoid adsorption of aprotinin onto negatively charged solid phases, e.g., chromatography gels, ultrafiltration membranes, the NaCl concentration should be above 0.1 M or other suitable salts should be added to all buffers used during the separation.
Storage conditions (working solution): -15 to -25 °C

Freely soluble in water (10 mg/ml) or aqueous buffer solution (e.g., Tris, 0.1 M, pH 8.0). A solution adjusted to pH 7 to 8 is stable for approximately 1 week at 2 to 8 °C.
Aliquots stored at -15 to -25 °C are stable for approximately 6 months.
Note: Avoid repeated freezing and thawing and exposure to strongly alkaline solutions (inactive at pH > 12.8).

For life science research only. Not for use in diagnostic procedures.