Intestinal mucosal hydrolysis of proteins and peptides.

The major products of intraluminal hydrolysis of dietary proteins appear to be small peptides and amino acids. Recent studies indicate that the distal part of the small intestine may play an important role in the digestion and absorption of dietary proteins. Intestinal mucosal cellular hydrolysis of peptides and proteins represents the terminal stage of digestion of dietary proteins and appears to be carried out predominantly by amino-oligopeptidases in brush border membranes and cytoplasm. These enzymes in the two main subcellular loci are distinct since they exhibit different electrophoretic mobilities, physicochemical properties, substrate specificities and responses to starvation and dietary manipulation. Two amino-oligopeptidases have been purified from the intestinal brush border of the rat. The enzymes are remarkably similar to each other in many respects. They have an apparent molecular weight of 280 000 and are composed of two subunits of equal molecular weight. Both enzymes are glycoproteins having similar chemical compositions, common antigenic properties, substrate specificities and kinetic properties.