Börner V, Fei Y J, Hartrodt B, Ganapathy V, Leibach F H, Neubert K, Brandsch M
Institute of Biochemistry, Department of Biochemistry/Biotechnology, Martin-Luther-University Halle-Wittenberg, Germany.
Eur J Biochem. 1998 Aug 1;255(3):698-702. doi: 10.1046/j.1432-1327.1998.2550698.x.
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.
在Caco-2细胞以及表达人肽转运体1（PEPT1）的非洲爪蟾卵母细胞中，对肠道H⁺/肽同向转运体（PEPT1）转运氨基酸芳基酰胺的情况进行了研究。几种氨基酸酰胺能够抑制Caco-2细胞对[¹⁴C]甘氨酰肌氨酸的摄取。丙氨酸-4-硝基苯胺（Ki = 0.08 mM）、苯丙氨酸-4-硝基苯胺（Ki = 0.09 mM）和丙氨酸-4-苯基苯胺（Ki = 0.03 mM）被视为底物，其亲和力与天然丙氨酸-Xaa二肽相当或更高。丙氨酸苯胺（Ki = 2.9 mM）、丙氨酸-7-氨基-4-甲基香豆素（Ki = 0.2 mM）、丙氨酸-4-氯苯胺（Ki = 0.3 mM）和丙氨酸-4-甲基苯胺（Ki = 0.3 mM）也被PEPT1识别为底物。相比之下，丙氨酸、丙氨酰胺、苯丙氨酰胺、丙氨酸甲酯、丙氨酸-4-硝基苄酯和丙氨酸甲酰胺未被识别（Ki > 20 mM）。在非洲爪蟾卵母细胞中，丙氨酸-4-硝基苯胺、丙氨酸-7-氨基-4-甲基香豆素、丙氨酸-4-甲基苯胺和丙氨酸苯胺的转运与正电荷转移相关，且电流相对于底物浓度呈饱和状态（K0.5值分别为：0.1、0.2、0.8和3.1 mM）。丙氨酸-4-甲基苯胺诱导的电流相对于底物浓度呈饱和状态，并受膜电位影响。还发现转运体对丙氨酸-4-甲基苯胺的亲和力也受膜电位影响。我们得出结论，肠道H⁺/肽共转运系统PEPT1将氨基酸芳基酰胺作为底物。
