Unit definition: One trypsin unit will produce a ΔA253 of 0.001 per min with BAEE as substrate at pH 7.6 at 25 °C; reaction volume 3.2 ml, 1 cm light path.
M.W.: 7.8 kDa
The Bowman-Birk inhibitor (BBI) from soybean is a monomeric protein containing 71 amino acids in a single polypeptide chain crosslinked by seven disulfide bridges. This inhibitor contains two independent inhibitory binding sites, one for trypsin and the other for chymotrypsin. BBI binds each protease to form a 1:1 complex. Since the inhibition is non-competitive, BBI has the ability to form a ternary complex with both enzymes.
Specific Activity: One mg protein will inhibit ≥2 mg trypsin with activity of ~10,000 BAEE units per mg protein.
One mg protein will inhibit ≥2.0 mg chymotrypsin with activity of ~40 BTEE units per mg protein.
Solubility: Trypsin-chymotrypsin inhibitor is soluble in water or 0.67M Sodium phosphate, pH 7.6 (1 mg/ml).