The intestinal di/tri-peptide transporter 1 (hPEPT1) has been suggested as a drug delivery target for peptide-based prodrugs. The aim of the study was to synthesize a series of 11 serine-containing dipeptides (H-X(aa)-Ser-OH) and to investigate the relationship between binding to and transport via hPEPT1. An additional aim was to design a dipeptide which could serve as a pro-moiety for prodrugs targeted to hPEPT1. X(aa) was chosen from the 20 proteogenic amino acids. The dipeptides were synthesized using solid phase peptide synthesis. The K(i)-values of H-X(aa)-Ser-OH dipeptides for hPEPT1 in MDCK/hPEPT1 cells ranged from 0.14 mM (logIC(50)=-0.85 ± 0.06) for H-Tyr-Ser-OH to 0.89 mM (logIC(50)=-0.09 ± 0.02) for H-Gly-Ser-OH, as measured in a competition assay with [(14)C]Gly-Sar. The dipeptides were translocated via hPEPT1 with K(m)-values in the range of 0.20 (logIC(50)=-0.69 ± 0.04) for H-Met-Ser-OH to 1.04 (logIC(50)=0.02 ± 0.04) mM for H-Gly-Ser-OH. The relationship between ligand and transportate properties indicated that the initial binding of the ligand to hPEPT1 is the major determinant for translocation of the investigated dipeptides. H-Phe-Ser-OH was selected as a pro-moiety, and two prodrugs were synthesized, i.e. H-Phe-Ser(Ibuprofyl)-OH and H-Phe-Ser(Bz)-OH. Both H-Phe-Ser(Ibuprofyl)-OH and H-Phe-Ser(Bz)-OH had high affinity for hPEPT1 with K(i)-values of 0.07 mM (logIC(50)=-0.92 ± 0.12) and 0.12 mM (logIC(50)=-1.17 ± 0.40), respectively. However, none of the prodrugs were translocated via hPEPT1. This indicated that the coupling of the drug compounds to the peptide backbone did not decrease transporter binding, but abolished translocation, and that high affinity of prodrugs does not necessarily translate into favourable permeation properties.

中文翻译：

---

HX aa-Ser-OH二肽通过hPEPT1的亲和力和易位关系：评估H-Phe-Ser-OH作为布洛芬和苯甲酸前药的促成部分。

肠道二/三肽转运蛋白1（hPEPT1）已被建议作为基于肽的前药的药物递送靶标。该研究的目的是合成一系列11种含丝氨酸的二肽（HX（aa）-Ser-OH），并研究与hPEPT1的结合和转运之间的关系。另一个目的是设计一种二肽，该二肽可以用作靶向hPEPT1的前药的前半部分。X（aa）选自20个蛋白质氨基酸。使用固相肽合成法合成二肽。MDCK / hPEPT1细胞中hPEPT1的HX（aa）-Ser-OH二肽的K（i）值范围从H-Tyr-Ser-OH的0.14 mM（logIC（50）=-0.85±0.06）到0.89 mM H-Gly-Ser-OH的（logIC（50）=-0.09±0.02），是在与[（14）C] Gly-Sar的竞争分析中测得的。通过hPEPT1将二肽以K（m）值在H-Met-Ser-OH的0.20（logIC（50）=-0.69±0.04）范围内移位到1.04（logIC（50）= 0.02±0.04）mM用于H-Gly-Ser-OH。配体与转运性质之间的关系表明，配体与hPEPT1的初始结合是所研究二肽易位的主要决定因素。选择H-Phe-Ser-OH作为前部分，并合成了两种前药，即H-Phe-Ser（布洛菲基）-OH和H-Phe-Ser（Bz）-OH。H-Phe-Ser（异丁烯丙基）-OH和H-Phe-Ser（Bz）-OH对hPEPT1都具有高亲和力，K（i）值为0.07 mM（logIC（50）=-0.92±0.12）和0.12 mM（logIC（50）=-1.17±0.40）。但是，没有任何前药通过hPEPT1转运。