Tiruppathi C, Ganapathy V, Leibach F H
Department of Cell and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
J Biol Chem. 1990 Sep 5;265(25):14870-4.
We investigated the interaction between glycylsarcosine (Gly-Sar), a neutral dipeptide, and phenylalanylprolylalanine (Phe-Pro-Ala), a neutral tripeptide, for transport into renal brush-border membrane vesicles isolated from Japanese F344 rats. This rat strain is genetically deficient in dipeptidylpeptidase IV. Owing to the absence of this enzyme, Phe-Pro-Ala was found to be completely resistant to hydrolysis by the brush-border membranes, and this enabled us to study the uptake of the intact tripeptide without interference by hydrolysis. Gly-Sar was also resistant to hydrolysis by these membrane preparations. Transport of Gly-Sar as well as that of Phe-Pro-Ala in these vesicles was driven by an inwardly directed H+ gradient. Gly-Sar transport was blocked completely by increasing concentrations of Phe-Pro-Ala and vice versa. Gly-Sar inhibited Phe-Pro-Ala transport competitively; and similarly, Phe-Pro-Ala inhibited Gly-Sar transport competitively. The dissociation constant (Kt) for Gly-Sar transport (94 +/- 5 microM) was very similar to the inhibition constant (Ki) for Gly-Sar to inhibit Phe-Pro-Ala transport (107 +/- 13 microM). The Kt for Phe-Pro-Ala transport (36 +/- 3 microM) was equal to the Ki for Phe-Pro-Ala to inhibit Gly-Sar transport (36 +/- 6 microM). Furthermore, linear correlation was exhibited by various neutral di- and tripeptides, which were also resistant to hydrolysis, in their abilities to inhibit the transport of Gly-Sar and that of Phe-Pro-Ala. These results strongly suggest that a common carrier system participates in the transport of neutral di- and tripeptides in renal brush-border membrane vesicles.
我们研究了中性二肽甘氨酰肌氨酸（Gly-Sar）与中性三肽苯丙氨酰脯氨酰丙氨酸（Phe-Pro-Ala）之间的相互作用，以研究它们转运至从日本F344大鼠分离的肾刷状缘膜囊泡中的情况。该大鼠品系在二肽基肽酶IV方面存在基因缺陷。由于缺乏这种酶，发现Phe-Pro-Ala对刷状缘膜的水解作用完全具有抗性，这使我们能够研究完整三肽的摄取，而不受水解作用的干扰。Gly-Sar对这些膜制剂的水解作用也具有抗性。这些囊泡中Gly-Sar以及Phe-Pro-Ala的转运由内向的H⁺梯度驱动。随着Phe-Pro-Ala浓度增加，Gly-Sar的转运被完全阻断，反之亦然。Gly-Sar竞争性抑制Phe-Pro-Ala的转运；同样，Phe-Pro-Ala也竞争性抑制Gly-Sar的转运。Gly-Sar转运的解离常数（Kt）（94±5微摩尔）与Gly-Sar抑制Phe-Pro-Ala转运的抑制常数（Ki）（107±13微摩尔）非常相似。Phe-Pro-Ala转运的Kt（36±3微摩尔）等于Phe-Pro-Ala抑制Gly-Sar转运的Ki（36±6微摩尔）。此外，各种对水解作用也具有抗性的中性二肽和三肽在抑制Gly-Sar和Phe-Pro-Ala转运的能力方面呈现出线性相关性。这些结果有力地表明，一个共同的载体系统参与了肾刷状缘膜囊泡中中性二肽和三肽的转运。
