β- and γ-Di- and Tripeptides as Potential Substrates for the Oligopeptide Transporter hPepT1

The hPepT1-mediated transport properties of a series of 11 synthesized beta- and gamma-peptides have been studied in Caco-2 cells. The results show that several of the compounds interact with the peptide transporter, but only two beta-dipeptides act as substrates and are transported across the cell monolayers. These two are less-efficient substrates than alpha-peptides. Larger derivatives than beta-dipeptides do not act as hPepT1 substrates, but instead, they appear to be substrates for P-glycoprotein efflux.