Kinetics and characteristics of absorption from an equimolar mixture of 12 glycyl-dipeptides in human jejunum.
We have investigated rates of dipeptide disappearance during jejunal perfusion with an equimolar mixture of 12 glycyl-dipeptides and compared amino acid absorption rates from this mixture with those from the corresponding free amino acid mixture in healthy volunteers. All dipeptides contained glycine in the N-terminal position, which was designed to favor peptide absorption rather than hydrolysis. At 2 mM concentration there was little difference in disappearance among dipeptides, but at 6 mM there was some selectivity: Gly-Phe and Gly-Met exhibited the fastest, and Gly-Arg and Gly-His the slowest rates of disappearance. However, between these ends of the spectrum there were only modest differences in disappearance among dipeptides (Gly-Ala, Gly-Thr, Gly-Leu, Gly-Ile, Gly-Val, Gly-Lys, Gly-Pro, Gly-Trp). The amino acid absorption rates were generally smaller but more selective from the free amino acid than from the dipeptide mixture. We conclude that (a) the C-terminal amino acid residue influences intestinal assimilation of glycyl-dipeptides and (b) the considerably greater absorption rate of amino acids from the dipeptide than from the amino acid mixture appears to be the result of uptake by a system that has a greater transport capacity than amino acid carrier systems, thus minimizing competition among its substrates.
D000328:Adult; D000596:Amino Acids / Q000378:metabolism; D001692:Biological Transport; D004151:Dipeptides / Q000378:metabolism*; D005260:Female; D005526:Food, Formulated; D005998:Glycine / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D007583:Jejunum / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009584:Nitrogen / Q000378:metabolism
D000596:Amino Acids; D004151:Dipeptides; D009584:Nitrogen; D005998:Glycine