Heat-Labile Growth-Inhibiting Factors in Beans (Phaseolus vulgaris)

Abstract

A comparative study in vitro was made of enzyme-inhibiting and hemagglutinin activities, and the effect on rat growth of 5 varieties of kidney beans (Phaseolus vulgaris). Extracts of 2 bean samples were active in agglutinating rabbit blood cells and toxic when fed to growing rats. Diets prepared with these seeds supplemented with methionine caused weight loss and death when fed to rats alone or with a supplement of 10% enzymatically or acid-digested casein. Hemagglutinating activity was observed in the feces of rats fed the raw bean diets. The possibility that the hemagglutinins are at least partly responsible for the toxic effects was examined. Three other samples of kidney beans had no significant hemagglutinating or lethal effect. Rats fed the raw seed meals supplemented with methionine did not gain weight but grew well with a similar diet supplemented with enzymatically digested casein. Supplements of 10% casein, 1% Na glutamate, or 10% acid-digested casein did not improve growth significantly but the latter did when tryptophan was added. Anti-trypsin and antiamylase activities were low or absent in some of the seeds and high in others, and did not appear to be directly related to the growth inhibition observed. The low growth-promoting action of the hemagglutinin-free beans might be explained by low digestibility and an enzyme-inhibiting activity of the bulk proteins different from that of the trypsin or amylase inhibitors.