Exploration of the Role of Phenylalanine in the Thrombin Receptor Tethered-Ligand Peptide by Substitution with a Series of Trifluorophenylalanines
作者:Ayami Matsushima、Tsugumi Fujita、Kazushi Okada、Naoto Shirasu、Takeru Nose、Yasuyuki Shimohigashi
DOI:10.1246/bcsj.73.2531
日期:2000.11
The thrombin receptor-tethered ligand SFLLRNP (abbreviation formed by one letter amino acid codes expressing Ser-Phe-Leu-Leu-Arg-Asn-Pro) consists of the Phe-2 residue essential for the receptor activation. In order to explore the molecular characteristics of this Phe-2-phenyl, a series of trifluorophenylalanines [(F3)Phe] was incorporated into this S/Phe/LLRNP for evaluation of their ability to induce the human platelet aggregation. A complete set of (F3)Phe in the L-configuration, namely, (2,3,4-F3)Phe, (2,3,5-F3)Phe, (2,3,6-F3)Phe, (2,4,5-F3)Phe, (2,4,6-F3)Phe, and (3,4,5-F3)Phe, was prepared from trifluorobenzyl bromides and diethyl acetamidomalonate. S/(2,3,4-F3)Phe/LLRNP was equipotent to S/Phe/LLRNP, while (2,4,5-F3)Phe-containing analog was almost twice as potent as those. (2,4,6-F3)Phe-analog exhibited about a half of the activity of S/Phe/LLRNP. (3,4,5-F3)Phe-, (2,3,5-F3)Phe-, and (2,3,6-F3)Phe-analogs were very weak. The analysis of these assay results suggested that Phe-2-phenyl of SFLLRNP is in the edge-to-face CH/π interaction with the receptor aromatic group, utilizing the Phe-2-phenyl edge along with benzene hydrogens at position 2-3 or 5-6. The computer-assisted semi-empirical molecular orbital calculations by MOPAC showed that the fluorine atom decreases the electron density of its ortho, meta, and para hydrogens, and thus increases their acidity more strongly in that order. All these suggested that H → F replacements reinforce the edge-to-face CH/π interaction to enhance biological activity. The H → F replacement on the Phe-phenyl group was found to render an effective structural examination; i.e., to identify the hydrogens in the CH/π interaction, and to intensify the CH/π interaction.
凝血酶受体束缚配体 SFLLRNP(由表达 Ser-Phe-Leu-Leu-Arg-Asn-Pro 的单字母氨基酸代码组成的缩写)由受体激活所必需的 Phe-2 残基组成。为了探索该 Phe-2-苯基的分子特征,将一系列三氟苯丙氨酸 [(F3)Phe] 掺入该 S/Phe/LLRNP 中,以评估其诱导人血小板聚集的能力。 L构型的完整(F3)Phe组,即(2,3,4-F3)Phe、(2,3,5-F3)Phe、(2,3,6-F3)Phe、( 2,4,5-F3)Phe、(2,4,6-F3)Phe 和 (3,4,5-F3)Phe 由三氟苄基溴和乙酰胺丙二酸二乙酯制备。 S/(2,3,4-F3)Phe/LLRNP 与 S/Phe/LLRNP 等效,而含有 (2,4,5-F3)Phe 的类似物几乎是其两倍。 (2,4,6-F3)Phe 类似物表现出大约 S/Phe/LLRNP 一半的活性。 (3,4,5-F3)Phe-、(2,3,5-F3)Phe-和(2,3,6-F3)Phe-类似物非常弱。对这些测定结果的分析表明,SFLLRNP 的 Phe-2-苯基与受体芳香基团以边对面的 CH/π 相互作用,利用 Phe-2-苯基边缘以及 2-3 位的苯氢。或5-6。 MOPAC 的计算机辅助半经验分子轨道计算表明,氟原子降低了其邻氢、间氢和对氢的电子密度,从而按顺序更强烈地增加了它们的酸性。所有这些表明H → F 替换增强了边对面的CH/π 相互作用,从而增强了生物活性。发现 Phe-苯基上的 H → F 取代可以进行有效的结构检查;即识别CH/π相互作用中的氢,并加强CH/π相互作用。