Ramamoorthy S, Liu W, Ma Y Y, Yang-Feng T L, Ganapathy V, Leibach F H
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912, USA.
Biochim Biophys Acta. 1995 Nov 22;1240(1):1-4. doi: 10.1016/0005-2736(95)00178-7.
We report here on the functional characterization of the H+/peptide cotransporter PEPT 2 cloned from human kidney and on the chromosomal localization of the PEPT 2 gene. PEPT 2, when functionally expressed in HeLa cells, induces the transport of the neutral dipeptide glycylsarcosine. The induced transport activity is markedly influenced by extracellular pH. The optimum pH for the transport process is 6.0-7.0. Kinetic analysis has revealed that PEPT 2 is a high-affinity transporter, the Michaelis-Menten constant for glycylsarcosine being 74 +/- 14 microM. The human intestinal H+/peptide cotransporter PEPT 1 has 4-fold less affinity for the dipeptide under identical experimental conditions. Studies with other chemically diverse dipeptides have established that PEPT 2 possesses higher affinity than PEPT 1 not only for neutral peptides but also for peptides consisting of anionic and/or cationic amino acids. Somatic cell hybrid analysis and in situ hybridization have shown that the gene encoding PEPT 2 maps to human chromosome 3q13.3-q21.
我们在此报告从人肾克隆的H⁺/肽共转运体PEPT 2的功能特性以及PEPT 2基因的染色体定位。当在HeLa细胞中功能性表达时，PEPT 2可诱导中性二肽甘氨酰肌氨酸的转运。诱导的转运活性受到细胞外pH的显著影响。转运过程的最佳pH为6.0 - 7.0。动力学分析表明，PEPT 2是一种高亲和力转运体，甘氨酰肌氨酸的米氏常数为74±14μM。在相同实验条件下，人肠道H⁺/肽共转运体PEPT 1对该二肽的亲和力低4倍。对其他化学结构不同的二肽的研究表明，PEPT 2不仅对中性肽，而且对由阴离子和/或阳离子氨基酸组成的肽具有比PEPT 1更高的亲和力。体细胞杂交分析和原位杂交表明，编码PEPT 2的基因定位于人染色体3q13.3 - q21。
