Division of Bioresources and Bioenvironmental Sciences, Faculty of Agriculture, Graduate School, Kyushu University , 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
J Agric Food Chem. 2016 Mar 16;64(10):2072-9. doi: 10.1021/acs.jafc.6b00279. Epub 2016 Mar 4.
Glycyl-sarcosine (Gly-Sar) is a well-known model substrate for the intestinal uptake of dipeptides through peptide transporter 1 (PepT1). However, there are no other model peptides larger than tripeptides to evaluate their intestinal transport ability. In this study, we designed new oligopeptides based on the Gly-Sar structure in terms of protease resistance. Gly-Sar-Sar was found to be an appropriate transport model for tripeptides because it does not degrade during the transport across the rat intestinal membrane, while Gly-Gly-Sar was degraded to Gly-Sar during the 60 min transport. Caco-2 cell transport experiments revealed that the designed oligopeptides based on Gly-Sar-Sar showed a significantly (p < 0.05) lower transport ability by factors of 1/10-, 1/25-, and 1/40-fold for Gly-Sar-Sar, Gly-Sar-Sar-Sar, and Gly-Sar-Sar-Sar-Sar, respectively, compared to Gly-Sar (apparent permeability coefficient: 38.6 ± 11.4 cm/s). Cell experiments also showed that the designed tripeptide and Gly-Sar were transported across Caco-2 cell via PepT1, whereas the tetra- and pentapeptides were transported through the paracellular tight-junction pathway.
甘氨酰-肌氨酸（Gly-Sar）是一种众所周知的模型底物，可通过肽转运蛋白 1（PepT1）来吸收肠道中的二肽。然而，目前还没有其他大于三肽的模型肽来评估它们的肠道转运能力。在本研究中，我们根据蛋白酶抗性从 Gly-Sar 结构设计了新的寡肽。甘氨酰-肌氨酰-肌氨酸（Gly-Sar-Sar）被发现是一种合适的三肽转运模型，因为它在穿过大鼠肠膜的转运过程中不会降解，而甘氨酰-甘氨酰-肌氨酸（Gly-Gly-Sar）在 60 分钟的转运过程中会降解为甘氨酰-肌氨酸（Gly-Sar）。Caco-2 细胞转运实验表明，基于 Gly-Sar-Sar 设计的寡肽的转运能力明显（p<0.05）降低，与甘氨酰-肌氨酸（Gly-Sar）相比，其分别降低了 1/10、1/25 和 1/40 倍，对于 Gly-Sar-Sar-Sar、Gly-Sar-Sar-Sar-Sar 和 Gly-Sar-Sar-Sar-Sar-Sar。（表观渗透系数：38.6±11.4cm/s）。细胞实验还表明，设计的三肽和甘氨酰-肌氨酸通过 PepT1 转运穿过 Caco-2 细胞，而四肽和五肽则通过细胞旁紧密连接途径转运。
