Cancer chymotrypsin inhibitor

The Bowman-Birk soybean trypsin and chymotrypsin inhibitor modulates the growth of human colon and breast cancer cells. 

Protease inhibitors in soybeans, known as trypsin inhibitors (TIs), play important roles in nutritional properties of soybeans and soy protein products. Two types of TI are the Kunitz inhibitor and the Bowman-Birk inhibitor. The Kunitz inhibitor has a MW of 21,500 with two disulfide bonds, while the Bowman-Birk inhibitor has a MW of 7,900 with seven disulfide bonds (Wolf, 1977). The large ratio of disulfide bonds to MW in the Bowman-Birk inhibitor stabilizes protein conformation and makes the Bowman-Birk inhibitor highly resistant to heat denaturation and inactivation. The Kunitz inhibitor inhibits trypsin, while the Bowman-Birk inhibitor inhibits both trypsin and chymotrypsin. The kinetics of TI inactivation when heating at high water activity were determined by Johnson et al. (1980) they estimated that 83-91% of the TI activity in soybeans is due to the Kunitz inhibitor. Recently, the Bowman-Birk inhibitor was attributed cancer-protecting qualities and also interest exists in using purified soy TI to treat AIDS patients (Kennedy, 1995, 1998 Kennedy Szuhaj, 1994). 

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