The AAPS Journal

, Volume 12, Issue 3, pp 385–396 | Cite as

A Quantitative Structure–Activity Relationship for Translocation of Tripeptides via the Human Proton-Coupled Peptide Transporter, hPEPT1 (SLC15A1)

  • Diana Højmark Omkvist
  • Simon Birksø Larsen
  • Carsten Uhd Nielsen
  • Bente Steffansen
  • Lars Olsen
  • Flemming Steen Jørgensen
  • Birger BrodinEmail author
Research Article


The human intestinal proton-coupled peptide transporter, hPEPT1 (SLC15A1), has been identified as an absorptive transporter for both drug substances and prodrugs. An understanding of the prerequisites for transport has so far been obtained from models based on competition experiments. These models have limited value for predicting substrate translocation via hPEPT1. The aim of the present study was to investigate the requirements for translocation via hPEPT1. A set of 55 tripeptides was selected from a principal component analysis based on VolSurf descriptors using a statistical design. The majority of theses tripeptides have not previously been investigated. Translocation of the tripeptides via hPEPT1 was determined in a MDCK/hPEPT1 cell-based translocation assay measuring substrate-induced changes in fluorescence of a membrane potential-sensitive probe. Affinities for hPEPT1 of relevant tripeptides were determined by competition studies with [14C]Gly-Sar in MDCK/hPEPT1 cells. Forty tripeptides were found to be substrates for hPEPT1, having K m app values in the range 0.4–28 mM. Eight tripeptides were not able to cause a substrate-induced change in fluorescence in the translocation assay and seven tripeptides interacted with the probe itself. The conformationally restricted tripeptide Met-Pro-Pro was identified as a novel high-affinity inhibitor of hPEPT1. We also discovered the first tripeptide (Asp-Ile-Arg) that was neither a substrate nor an inhibitor of hPEPT1. To rationalise the requirements for transport, a quantitative structure–activity relationship model correlating K m app values with VolSurf descriptors was constructed. This is, to our knowledge, the first predictive model for the translocation of tripeptides via hPEPT1.

Key words

FLIPR membrane potential assay PEPT1 (SLC15A1) QSAR translocation tripeptides 



This project was funded by grants from The Novo Nordisk PhD plus Prize and the Carlsberg Foundation. The excellent technical support of Bettina Dinitzen, Birgitte Eltong and Maria D. Læssøe Pedersen is highly appreciated.


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Copyright information

© American Association of Pharmaceutical Scientists 2010

Authors and Affiliations

  • Diana Højmark Omkvist
    • 1
  • Simon Birksø Larsen
    • 2
  • Carsten Uhd Nielsen
    • 1
  • Bente Steffansen
    • 1
  • Lars Olsen
    • 2
  • Flemming Steen Jørgensen
    • 2
  • Birger Brodin
    • 1
    Email author
  1. 1.Drug Transporters in ADME, Department of Pharmaceutics and Analytical ChemistryUniversity of CopenhagenCopenhagenDenmark
  2. 2.Biostructural Research, Department of Medicinal Chemistry, The Faculty of Pharmaceutical SciencesUniversity of CopenhagenCopenhagenDenmark

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