The nutritional significance of plant protease inhibitors.

It has been recognized for many years that the nutritive value and protein digestibility of many plant proteins, particularly those derived from legumes, are very poor unless subjected to cooking or some other form of heat treatment (Liener & Kakade, 1969). This beneficial effect of heat has beem generally attributed, at least in part, to the destruction of a unique class of proteins which have the ability to combine in a very specific fashion with the enzymes (trypsin and chymotrypsin) which play a key role in the digestion of proteins in the intestinal tract of animals. Elucidation of the precise manner in which these so-called protease inhibitors lead to growth inhibition, however, has proved to be more elusive than might be suggested by this simple concept. The situation is further complicated by the fact that factors other than the protease inhibitors may affect the digestibility of dietary proteins. Interest in the nutritional role of the protease inhibitors has continued to mount largely as a consequence of the recent introduction of textvizsd vegetable proteins as a possible substitute for meat protein in the human diet. This paper will address itself to a consideration of the mode of action of the protease inhibitors and the implications this may have with respect to the consumption of plant proteins by humans.