Protease inhibitors from broad bean isolation and purification

Four protease inhibitors were demonstrated and two, BBPI-1 and BBPI-2, were purified from broad bean seeds using a combination of (NH₄)₂SO₄ fractionation, ion-exchange chromatography on CM 52-cellulose and CM 50 Sephadex. BBPI-1 and 2 had broad specificity and inhibited trypsin, chymotrypsin, thrombin, pronase and papain. Both inhibitors were heat stable, had a wide pH tolerance, a MW of approximately 11 000 and contained 14·5% N. BBPI-1 and 2 had a pI of 8·5 and 7·5 respectively.