Objectives: The proton-coupled amino acid transporter 1, hPAT1 is an absorptive transporter situated in the apical membrane of epithelial cells throughout the small intestine. Substrates are generally amino acids, such as L- Pro, Gly and GABA, but recently we have also identified the dipeptidomimetic drug substance 5- aminolevulenic acid (ALA) as a substrate for hPAT1, hence the aim of the present study was to investigate if the N-methylated dipeptide Gly- Sar also is a hPAT1 substrate. Methods: Transport of Gly-Sar via hPAT1 was measured by two-electrode voltage clamp on hPAT1 cRNA injected X. Laevis oocytes or by apical [14C]Gly- Sar uptake in Caco-2 cells. Oocytes were clamped at a membrane potential of -60 mV and water injected oocytes served as negative control. Uptake was measured in the absence or presence of 5-hydroxy-L-tryptophan (5-HTP) as a control for inhibition of Gly-Sar transport via hPAT1 or L-4,4'-Biphenylalanyl-L-Proline (Bip-Pro) as control for inhibition of transport via the human peptide transporter 1, hPEPT1 (SLC15A1). Results: In hPAT1 expressing oocytes concentration-dependent inward current were caused by Gly-Sar (Km = 49 +/­ 9 mM), ALA (Km = 15 +/­ 1.6 mM), GABA (Km = 2.4 +/­ 0.28 mM), L- Pro (Km = 1.8 +/­ 0.17 mM) and Gly (Km = 11.4 +/­ 1.0 mM), whereas 20 mM of Val, Leu, mannitol and 10 mM of 5-HTP did not evoke inward currents. In Caco-2 cell monolayers the apical uptake of 30 mM Gly-Sar was inhibited by 22 and 21 % in the presence of 5-HTP or Bip-Pro, respectively, and by 60 % in the presence of both. Conclusion: The results show that Gly-Sar is a substrate for hPAT1, although with a lower affinity than typical hPAT1 substrates. In Caco- 2 cells 30 mM Gly-Sar is transported via both hPAT1 and hPEPT1, and at this concentration both transporters seem equally important. In conclusion this annotates a new class of compounds as substrates for hPAT1 as well as demonstrates a substrate overlap for the two intestinal transporters hPAT1 and hPEPT1.