Transport of amino acid aryl amides by the intestinal H+/peptide cotransport system, PEPT1

Authors


  • Correspondence to M. Brandsch, Biozentrum of the Martin-Luther-University Halle-Wittenberg, c/o Department of Biochemistry/Biotechnology, Kurt-Mothes-Str. 3, D-06120 Halle, Germany

  • Fax: +49 345 552 7011.

  • E-mail:brandsch@biozentrum.uni-halle.de

  • URL:http://www.biochemtech.uni-halle.de

  • Abbreviations. Gly-Sar, glycylsarcosine; Ala-NH-Mec, Alanine 7-amido-4-methylcoumarin; NH-Np, 4-nitroanilide; OBzl, benzyl ester; IC50, concentration of unlabeled compound necessary to inhibit 50 % of radiolabeled Gly-Sar carrier-mediated uptake.

Abstract

Transport of amino acid aryl amides by the intestinal H+/peptide symporter (PEPT1) was studied in Caco-2 cells and in Xenopus laevis oocytes expressing human PEPT1. Several amino acid amides were able to inhibit the uptake of [14C]glycylsarcosine in Caco-2 cells. Ala-4-nitroanilide (Ki = 0.08 mM), Phe-4-nitroanilide (Ki = 0.09 mM) and Ala-4-phenylanilide (Ki = 0.03 mM) were accepted as substrates with equal or higher affinity than natural Ala-Xaa dipeptides. Ala-anilide (Ki = 2.9 mM), Ala-7-amido-4-methylcoumarin (Ki = 0.2 mM), Ala-4-chloroanilide (Ki = 0.3 mM) and Ala-4-methylanilide (Ki = 0.3 mM) were also recognized by PEPT1 as substrates. In contrast, alanine, Ala-amide, Phe-amide, Ala-methyl ester, Ala-4-nitrobenzyl ester and Ala-methylamide were not recognized (Ki > 20 mM). In X. laevis oocytes, transport of Ala-4-nitroanilide, Ala-7-amido-4-methylcoumarin, Ala-4-methylanilide and Ala-anilide was associated with transfer of positive charge and the currents were saturable with respect to substrate concentration (K0.5 values : 0.1, 0.2, 0.8 and 3.1 mM, respectively). The currents induced by Ala-4-methylanilide were saturable with respect to the substrate concentration and influenced by the membrane potential. The affinity of the transporter for Ala-4-methylanilide was also found to be influenced by the membrane potential. We conclude that the intestinal H+/peptide cotransport system PEPT1 accepts amino acid aryl amides as substrates.

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