Studies on the growth inhibitor fraction of Lima beans and isolation of a crystalline heat-stable trypsin inhibitor.

Ham and Sandstedt (2) and, subsequently, others have shown that there is a trypsin inhibitor in soy beans and other legumes which inhibits the growth of certain animals. At first it was believed that the components of beans which alter the nutritive value of proteins exert growth inhibition by their ability to inhibit proteolysis in the gastrointestinal tract. Recently Klose and associates (3) have demonstrated that the growthinhibitory fraction of Lima beans affects the growth of rats not by its action on proteolysis but by some other mechanism not yet identified. This conclusion was drawn because a diet including hydrolyzed proteins also resulted in a decrease of growth when supplemented with the growthinhibitory fraction. More recently Westfall and coworkers (4) came to similar conclusions after investigating the crude trypsin inhibitor fraction gd soy beans. The aim of the present report is to confirm the observations of the earlier investigators concerning the growth-inhibitory effect of the crude Lima bean fraction and to describe the isolation from this fraction of a crystalline, heat-stable globulin which powerfully inhibits trypsin and moderately inhibits chymotrypsin. Swiss mice, which were employed in the feeding experiments, were found to be extremely sensitive to the growth-inhibitory fraction of Lima beans.