Effect of Plant Proteins on Colonic Bacterial Fermentation and Pancreatic Proteases in Gnotobiotic Rats: Comparison with Animal Proteins

In the human diet, vegetables are recommended as an alternate source of proteins. Dietary proteins are metabolized by endogenous pancreatic and intestinal proteases. However, proteins resistant to enzyme hydrolysis or ingested in large amounts reach the large bowel (Combe et al, 1970). These undigested nitrogenous matters are metabolized by gut microflora (Salter, 1973; Combe et al, 1976; Yanagida et al, 1985) and produce a large variety of metabolites: short chain fatty acids (SCFA), ammonia, amines and various phenolic acids. Among SCFA., the branched-chain isobutyric and isovaleric acids arise from the breakdown of valine, leucine and isoleucine (Cummings and Bingham, 1987; Zarling and Ruchim, 1987). Ammonia is mostly an end-product of bacterial proteolytic activity due to a specific bacterial urease.