Characterization and nutritional significance of peptide transport in man.

An in vivo intestinal perfusion technique has been used to investigate the characteristics of di- and tripeptides absorption in man. The results suggest that the model peptides studied were absorbed by a transport system separate to those responsible for mediating absorption of free amino acids. Two modes of intestinal uptake have been identified, namely transport of unhydrolysed peptides and transport of free amino acid residues liberated from the peptides by the action of brush border peptidases. A consistent finding was that amino acid residues were absorbed more rapidly from di- and tripeptides than from free amino acids. When amino acid uptake from four partial enzymic hydrolysates of protein was investigated, the 'kinetic advantage' conferred by peptides on amino acid uptake was found to be a generalized and concentration-dependent phenomenon. As later test meal studies showed that orally administered peptide mixtures were assimilated at least as rapidly as free amino acid mixtures, serious consideration could be given to using the less hypertonic and more palatable oligopeptide-based nitrogen sources in chemically defined elemental diets.