The effect of conformation on the membrane permeation of coumarinic acid- and phenylpropionic acid-based cyclic prodrugs of opioid peptides
The effect of conformation on the membrane permeation of coumarinic acid- and phenylpropionic acid-based cyclic prodrugs of opioid peptides
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DOI：
10.1034/j.1399-3011.1999.00076.x
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发表时间：
1999-04-01
期刊：
影响因子：
--
通讯作者：
Borchardt, RT
中科院分区：
文献类型：
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作者：
Gudmundsson, OS;Jois, SDS;Borchardt, RT
在使用Caco-2细胞（肠粘膜的体外细胞培养模型）的早期研究中，我们已经表明基于香豆酸（3和4）和基于苯基丙酸（5和6）的环状前药比相应的阿片肽[Leu（5）]-脑啡肽更能够渗透细胞单层（1，H-Tyr-Gly-Gly-Phe-Leu-OH）和DADLE（2，H-Tyr-D-Ala-Gly-Phe-D-Leu-OH）。在试图解释的环状前药的渗透增加，我们已经确定了这些环状前药在溶液中的可能的构象，使用光谱技术（2D-NMR，CD）和分子动力学模拟。光谱和分子动力学研究表明，环状前药4在溶液中表现出两种主要构象（A和B）。构象异构体A在Tyr 1-D-Ala 2-Gly 3-Phe 4处表现出I型β-转角。转角的存在得到了D-Ala 2的NH和Gly 3的NH之间以及Gly 3的NH和Phe 4的NH之间的ROE交叉峰的支持。环状前药4的构象体B由在相同位置的II型β-转角组成。II型转弯通过氢键稳定，从而形成更紧凑的结构，而I型转弯没有表现出类似的分子内氢键。化合物3、5和6的光谱数据与这些环状前药具有与用环状前药4观察到的那些类似的溶液结构的结论一致。环状前药3-6中增加的亲脂性和明确的二级结构，但线性肽1和2中没有，都有助于这些前药渗透膜的能力增强。
In an earlier study using Caco-2 cells, an in vitro cell culture model of the intestinal mucosa, we have shown that the coumarinic-based (3 and 4) and the phenylpropionic acid-based (5 and 6) cyclic prodrugs were more able to permeate the cell monolayers than were the corresponding opioid peptides, [Leu(5)]-enkephalin (1, H-Tyr-Gly-Gly-Phe-Leu-OH) and DADLE (2, H-Tyr-D-Ala-Gly-Phe-D-Leu-OH). In an attempt to explain the increased permeation of the cyclic prodrugs, we have determined the possible conformations of these cyclic prodrugs in solution, using spectroscopic techniques (2D-NMR, CD) and molecular dynamics simulations. Spectroscopic as well as molecular dynamic studies indicate that cyclic prodrug 4 exhibits two major conformers (A and B) in solution. Conformer A exhibited a type I beta-turn at Tyr1-D-Ala2-Gly3-Phe4. The presence of a turn was supported by ROE cross-peaks between the NH of D-Ala2 and the NH of Gly3 and between the NH of Gly3 and the NH of Phe4. Conformer B of cyclic prodrug 4 consisted of type II beta-turns at the same positions. The type II turn was stabilized by hydrogen bonding, thus forming a more compact structure, whereas the type I turn did not exhibit similar intramolecular hydrogen bonding. Spectroscopic data for compounds 3, 5 and 6 are consistent with the conclusion that these cyclic prodrugs have solution structures similar to those observed with cyclic prodrug 4. The increased lipophilicity and well-defined secondary structures in cyclic prodrugs 3-6, but not in the linear peptides 1 and 2, could both contribute to the enhanced ability of these prodrugs to permeate membranes.