Transport Versus Hydrolysis: Reassessing Intestinal Assimilation of Di- and Tripeptides by LC-MS/MS Analysis

Mol Nutr Food Res. 2019 Nov;63(21):e1900263. doi: 10.1002/mnfr.201900263. Epub 2019 Aug 16.


Scope: The role of PEPT1 in the uptake of intact peptides as compared to hydrolysis prior to uptake of their constituents is unknown. Here, dipeptides, tripeptides, and amino acids are quantified to study the fate of selected peptides in different intestinal models.

Methods and results: An LC-MS/MS-based method is applied for the simultaneous assessment of rates of hydrolysis and transport of a peptide panel in Caco-2 transwell cell culture, in vitro and in vivo in mice expressing or lacking PEPT1, and in hydrolysis studies in vitro using human intestinal samples. It is shown that susceptibility to hydrolysis of peptides at the brush border membrane or within epithelial cells is practically identical in all tested models and strictly structure-dependent. Peptides with high luminal disappearance show substantial hydrolysis and low basolateral appearance, while peptides with low disappearance show strong PEPT1 dependency and high basolateral appearance in intact form in Caco-2 transwell culture.

Conclusion: Hydrolysis and transport of intact peptides are highly variable and structure-dependent. For peptides possessing less polar N-terminal residues, hydrolysis usually dominates over transport via PEPT1. For other peptides with high intrinsic hydrolysis resistance, including anserine, carnosine, ɣ-glutamyl-dipeptides, and aminocephalosporins, PEPT1 is the main determinant for appearance in peripheral blood.

Keywords: PEPT1; amino acids; peptidases; peptide transporters; protein digestion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / blood
  • Amino Acids / metabolism
  • Animals
  • Caco-2 Cells
  • Chromatography, Liquid
  • Dipeptides / blood
  • Dipeptides / metabolism
  • Dipeptides / pharmacokinetics
  • Female
  • Humans
  • Hydrolysis
  • Intestinal Absorption / physiology*
  • Intestinal Mucosa / drug effects
  • Intestinal Mucosa / metabolism
  • Male
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Peptide Transporter 1 / genetics
  • Peptide Transporter 1 / metabolism*
  • Peptides / chemistry
  • Peptides / metabolism*
  • Peptides / pharmacokinetics*
  • Protein Transport
  • Proteolysis
  • Tandem Mass Spectrometry


  • Amino Acids
  • Dipeptides
  • Peptide Transporter 1
  • Peptides
  • Slc15a1 protein, mouse
  • prolylglycine
  • glycylproline