Human and Clinical Nutrition Raw Soybeans Stimulate Human Pancreatic Proteinase Secretion1

Intraduodenal instillation of raw soybeans stimulated pancreatic proteinase secretion in humans. Raw soybeans almost abolished the activity of chymotrypsin and severely reduced (50%) the tryptic activity. Immunoreactivetryptic and chymotryptic ma terial simultaneouslyappeared in amounts 2 to 4 times basal concentrations. This increase, demonstrated with rocket immunoelectrophoresis, was begun within the first 10 min of soybean instillation. The enhanced se cretion also persisted throughout the succeeding saline instillation, and it is suggested that the presence of Kunitz trypsin inhibitor contributed to this postprandial stimulation. An amidase that hydrolyzeslow-molecular- weight substrates (i.e., benzoyl-argininep-nitroanilide) was found in raw soybeans. Its low activity was not assumed to substantially bias standard trypsin assays. The increased proteinase secretion was, as previously published, not preceded by an elevated plasma cholecystokinin concentration. The raw soybeans also caused a nonparallel secretion of amylase and protein- ases. Nervous, perhaps cholinergic,regulation mediates the inhibitor-stimulatedproteinase secretion in humans. This stimulation yields both a general increase of pro- teinases and also a specific inhibitor-resistant trypsin. This is consistent with the physiologic need for proenzyme-activationin the presence of inhibitors and for restoration of the proteolyticcapacity of the duodenal juice. J. Nutr. 122: 1407-1416, 1992.