Intestinal Assimilation of a Proline - containing Tetrapeptide ROLE OF A BRUSH

Address correspondence to Dr. Kim, Veterans Administration Medical Center. Received for publication 2 November 1982 and in revised form 4 April 1983. INTRODUCTION The final protein digestion products presented to the small intestine are free amino acids and small peptides consisting of two to six amino acids (1-4). The processes involved in the absorption of these final products after luminal proteolysis by pancreatic endoand exopeptidases are complex, but in most cases additional hydrolysis of these oligopeptides by brush border membrane peptidases is necessary before absorption by the intestinal enterocyte (5-9). Even though a variety of peptidases have been described as being localized to the intestinal brush border membrane (1020), only a few have been studied in any great detail (21, 22). Therefore, many of the biochemical and physiological events that occur during the final stages of digestion and absorption of peptides at the intestinal mucosal cell surface remain to be elucidated. Proline is found in a wide variety of dietary proteins, and the collagen molecule, for example, contains a significant amount of Gly-Pro in its amino acid sequence (23). In general, proline-containing peptides are resistant to hydrolysis by many of the known pancreatic and brush border membrane proteases (10, 22). Thus, the means by which these types of oligopeptides are hydrolyzed and assimilated by the intestinal enterocyte is of nutritional and physiological importance. In this report, the peptide Leu-Pro-Gly-Gly was used in order to further elucidate the mechanisms involved in the assimilation of proline-containing peptides by the intestine. With the use of an in vivo perfusion technique to closely approximate physiological conditions, we were able to demonstrate that intestinal 610 J. Clin. Invest. © The American Society for Clinical Investigation, Inc. * 0021-9738/83/08/0610/07 $1.00 Volume 72 August 1983 610-616 Downloaded from http://www.jci.org on December 20, 2017. https://doi.org/10.1172/JCI111009