Lima Bean Inhibitor: Lima bean trypsin inhibitor which inhibits bovine as well as human trypsin and plasmin, acts upon both trypsin and chymotrypsin by forming equimolar complexes. Lima bean inhibitors may be chromatographically separated into as many as six variants. Jones et al., Biochem., 2, 66, (1963) characterized four of them. All have similar but not identical amino acid composition, contain six or seven disulfide bonds and lack methionine and tryptophan. Molecular weights vary between 8 kDa and 10 kDa.
Ovomucoid: Ovomucoids are the glycoprotein protease inhibitors of avian egg white. There are several protease inhibitors in egg white. The Worthington product is that described by Lineweaver and Murray JBC, 171, 565 (1947). It has a molecular weight of approximately 28 kDa.
Pancreatic Inhibitor: The pancreatic inhibitor produced by Worthington is often referred to as the Kunitz inhibitor and was first crystallized by Kunitz and Northrop J. Gen. Physiol., 19, 991 (1936). It forms a very stable 1:1 complex with bovine trypsin between pH 3 and 10 and also with human trypsins. Chymotrypsin is also inhibited by this product but is bound less tightly. The esterolytic, proteolytic and elastolytic activities of porcine elastase, on the other hand, are not inhibited. The Kunitz inhibitor is a single polypeptide chain of 58 amino acids and has a molecular weight of 6.5 kDa. When lung tissue is used as the source, the inhibitor is called aprotinin.
Soybean Inhibitor: The soybean trypsin inhibitor was first crystallized by Kunitz in 1945 and is one of several such inhibitors found in soybeans. Its molecular weight is 21,500 ± 800 daltons and the optimum pH is 7.0. Soybean inhibitor inhibits trypsin mole-for-mole and to a lesser extent chymotrypsin.
Unit Definition: The activity of the inhibitors is expressed as the amount of twice crystallized trypsin (Worthington Code: TRL) inhibited per milligram of inhibitor. 1mg TRL ≥180 TAME units, 10,350 BAEE units, 3,450 USP/NF units.