Tateoka R, Abe H, Miyauchi S, Shuto S, Matsuda A, Kobayashi M, Miyazaki K, Kamo N
Laboratory of Biophysical Chemistry and Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, and Department of Pharmacy, Hokkaido University Hospital, Sapporo 060-8638 Japan.
Bioconjug Chem. 2001 Jul-Aug;12(4):485-92. doi: 10.1021/bc000135u.
Our previous paper [(1999) Bioconjugate Chem. 10, 24-31] pointed out that hydrophobicity of substrates/inhibitors plays an important role in the recognition by an oligopeptide transporter (PEPT1) expressed in the human intestinal epithelial cell line Caco-2. To determine the significance of that hydrophobicity, we have now synthesized dipeptide analogues conjugating the epsilon-amino group of Lys in Val-Lys with aliphatic carboxylic acids: acetic acid (C2), propanoic acid (C3), pentanoic acid (C5), hexanoic acid (C6), and decanoic acid (C10). The affinities of these conjugates were estimated by their inhibition of the accumulation rate of Gly-Sar, a well-established substrate for PEPT1. With the increase in length of the hydrocarbon chain of the conjugates, i.e., in the hydrophobicity of the conjugates, the inhibition strengthened. Dixon-Webb plot analysis of the inhibition by the C10-conjugated dipeptide showed competitive inhibition. The trans-stimulation effect of Val-Lys conjugated to C10 or C5 on the uptake of Ceftibuten was observed using rat brush border membrane vesicles. This findings showed that these conjugates are transportable substrates. These results confirmed that the hydrophobicity of substrates/inhibitor is one of the factors in the recognition by PEPT1.
我们之前的论文[（1999年）《生物共轭化学》10卷，24 - 31页]指出，底物/抑制剂的疏水性在人肠上皮细胞系Caco - 2中表达的寡肽转运体（PEPT1）的识别过程中起着重要作用。为了确定该疏水性的重要性，我们现在合成了将缬氨酸 - 赖氨酸中赖氨酸的ε - 氨基与脂肪族羧酸共轭的二肽类似物：乙酸（C2）、丙酸（C3）、戊酸（C5）、己酸（C6）和癸酸（C10）。通过这些共轭物对甘氨酸 - 肌氨酸（一种成熟的PEPT1底物）积累速率的抑制作用来估计它们的亲和力。随着共轭物碳氢链长度的增加，即共轭物疏水性的增加，抑制作用增强。对C10共轭二肽的抑制作用进行的狄克逊 - 韦布图分析显示为竞争性抑制。使用大鼠刷状缘膜囊泡观察到与C10或C5共轭的缬氨酸 - 赖氨酸对头孢布烯摄取的反式刺激作用。这些发现表明这些共轭物是可转运的底物。这些结果证实了底物/抑制剂的疏水性是PEPT1识别过程中的因素之一。
