Trypsin inhibitor from soybeans is a monomeric protein containing 181 amino acid residues in a single polypeptide chain crosslinked by two disulfide bridges.

• Reversible serine protease inhibitor
• Inhibits factor Xa, trypsin, chymotrypsin, kallikrein and plasmin
• One unit will inhibit one trypsin BAEE unit. One trypsin unit causes an increase of absorbance at 253 nm of 0.001 per minute at 25°C

Soybean trypsin inhibitor inhibits trypsin and to a lesser extent chymotrypsin and plasmin. It forms a 1:1 stoichiometric complex with trypsin. Upon formation of this complex, trypsin may cleave a single arginine-isoleucine bond in the inhibitor. Dissociation of this complex may yield the modified form or the native inhibitor. At the optimal pH for trypsin binding (pH 8.0), the association constant is ‰¥ 10x10⁸.

After trypsinizing cells, resuspend cells in 1 mL trypsin inhibitor solution (1mg/ml) for every mL of trypsin solution used for dissociation. Centrifuge the cell suspension at 1000 rpm for 5 minutes. A cell pellet should form. Remove as much of the trypsin inhibitor solution as possible and resuspend the pellet in serum-free medium. Culture cells as desired.