Hydrolysis of Dipeptides in Cells of the Small Intestine

Abstract

DURING the past few decades the mechanism of hydrolysis of peptides has been intensively investigated. An important outcome of these studies has been the establishment of the fact that the formation of amino-acids by the splitting of dipeptides does not occur in the cavity of the small intestine, but during the transport of peptides through the intestinal wall. The conclusion has been drawn, based on the analysis of correlation between the peptidase activity of the mucous liquid and homogenate of the intestine, that hydrolysis occurs intracellularly, that is, the peptides are passively transported through the membrane of the brush border into the cells of the small intestine, where they are split up into amino-acids^1,2. Data exist which suggest that this process occurs in the apical parts of the cytoplasm³. On the other hand, investigations of the effect of liquid convection relative to the surface of mucosa on the rate of hydrolysis of dipeptides⁴ have revealed that this process is more likely to be localized on the external surface of the cell membranes (membrane digestion) than within the cells.