Residual esterase activity of lima bean inhibitor-binding anhydrochymotrypsin preparations

A search for the source of the residual esterase activity of crude lima bean protease inhibitor-binding anhydrochymotrypsin preparations was undertaken. The preparations were found to contain about 40% of protein that possesses 1% (kc/Km) to 12% (kc) of the esterase activity of alpha-chymotrypsin. The active protein was isolated by affinity chromatography on soybean trypsin inhibitor-Sepharose. It appears to be an anhydroenzyme or a mixture of a limited number of anhydroenzymes in which a serine other than the catalytically essential serine-195 of the native enzyme has been converted to dehydroalanine.