Abstract: An assay of protease inhibitor activity was established on the basis of assay of trypsin and chymotrypsin activities. Three protease inhibitors, namely CM-BBI, crude-BBI and soy bean milk crystal crude-BBI, were determined by this method. Their activities (μg of enzyme used to inhibit one mg of inhibitor protein) were 16609, 1441 and 221 respectively. The ac tivity of the trypsin inhibitor from Sigma was also determined by our method. The result ob tained was identical with that of Sigma. Therefore, our method is highly reliabe. This method is an effective method for selecting the anticancer food.

Key words: protease inhibitor, trypsin, chymotrypsin