DIGESTIBILITY AND PROTEINASE INHIBITORY ACTION OF A KIDNEY BEAN GLOBULIN

A globulin fraction, isolated from black beans (Phaseolus vulgaris), was resistant to hydrolysis by pepsin, trypsin, chymotrypsin, papain, ficin, hurain, and subtilisin. After denaturation of the globulin by heat or urea, only slight hydrolysis by enzymes could be detected. The activity of all seven proteinases on their respective substrates was inhibited by the bean globulin. Preincubation of enzyme and globulin enhanced the inhibitory effect. When heat denatured, insoluble globulin was stirred with papain, proteolytic activity was diminished. The name globulin proteinase inhibitor is proposed for this factor. Adsorption with bentonite and celite of a crude bean extract eliminated the specific trypsin inhibitor activity but not that of the unspecific proteinase inhibitor. Trypsin inhibitor and proteinase inhibitor activities could also be separated by dialysis against distilled water, the former remaining in solution while the latter precipitated. The possible nutritional significances of these observations are discussed. © 1969, American Chemical Society. All rights reserved.