Metzner L, Neubert K, Brandsch M
Membrane Transport Group, Biozentrum, Martin-Luther-University Halle-Wittenberg, Halle, Germany.
Amino Acids. 2006 Sep;31(2):111-7. doi: 10.1007/s00726-005-0314-6. Epub 2006 May 15.
The proton coupled amino acid transporter PAT1 expressed in intestine, brain, and other organs accepts L- and D-proline, glycine, and L-alanine but also pharmaceutically active amino acid derivatives such as 3-amino-1-propanesulfonic acid, L-azetidine-2-carboxylic acid, and cis-4-hydroxy-D-proline as substrates. We systematically analyzed the structural requirements for PAT1 substrates by testing 87 amino acids, proline homologs, indoles, and derivatives. Affinity data and effects on membrane potential were determined using Caco-2 cells. For aliphatic amino acids, a blocked carboxyl group, the distance between amino and carboxyl group, and the position of the hydroxyl group are affinity limiting factors. Methylation of the amino group enhances substrate affinity. Hetero atoms in the proline template are well tolerated. Aromatic alpha-amino acids display low affinity. PAT1 interacts strongly with heterocyclic aromatic acids containing an indole scaffold. The structural requirements of PAT1 substrates elucidated in this study will be useful for the development of prodrugs.
质子偶联氨基酸转运体PAT1在肠道、大脑及其他器官中表达，它可接纳L-脯氨酸、D-脯氨酸、甘氨酸和L-丙氨酸，同时也能将诸如3-氨基-1-丙烷磺酸、L-氮杂环丁烷-2-羧酸和顺式-4-羟基-D-脯氨酸等具有药物活性的氨基酸衍生物作为底物。我们通过测试87种氨基酸、脯氨酸类似物、吲哚及衍生物，系统地分析了PAT1底物的结构要求。利用Caco-2细胞测定了亲和力数据及对膜电位的影响。对于脂肪族氨基酸而言，封闭的羧基、氨基与羧基之间的距离以及羟基的位置都是亲和力的限制因素。氨基甲基化可增强底物亲和力。脯氨酸模板中的杂原子具有良好的耐受性。芳香族α-氨基酸显示出低亲和力。PAT1与含有吲哚支架的杂环芳香酸强烈相互作用。本研究中阐明的PAT1底物的结构要求将有助于前体药物的开发。
