Ogawa T, Kodama H, Yoshioka K, Shimohigashi Y
Department of Chemistry, Faculty of Science, Fukuoka, Japan.
Pept Res. 1990 Jan-Feb;3(1):35-41.
Dipeptides containing 2,3-methanophenylalanine, a sterically constrained amino acid with alpha,beta-cyclopropane ring, showed fairly strong inhibitory activity for the hydrolysis of Ac-L-Tyr-OEt by chymotrypsin. Kinetic analyses of the inhibition by dipeptides, H-inverted delta E Phe-Leu (or Phe)-OMe (or OH), indicated the mode of inhibition to be competitive. Comparative analyses of the inhibitory constants Ki have clarified several structural elements necessary to elicit an inhibitory activity. Those include the (2R,3S)-configuration of the inverted delta E Phe residue, the phenyl side chain at position 2 and the C-terminal methylesterification. These structural conditions suggested that the peptides are in specific inhibitory conformation. In the conformational analyses of these dipeptide inhibitors by a high resolution 1H-NMR (270 MHz), the measurement of enhancements of the nuclear Overhauser effect indicated that an intramolecular hydrophobic bonding exists between the inverted delta Phe-phenyl and ester-methyl to construct the hydrophobic core in the molecule. It was suggested that this hydrophobic core interacts with the chymotrypsin S2 site and prevents the hydrolysis of methyl ester. The Leu2 or Phe2 interacts with the enzyme S1 site. The structure of dipeptides containing 2,3-methanophenylalanine has been characterized as an enzyme-inhibitory conformation that interacts with the enzyme at its catalytic center.
含有2,3-甲桥苯丙氨酸（一种具有α,β-环丙烷环的空间受限氨基酸）的二肽，对胰凝乳蛋白酶催化的Ac - L - 酪氨酸乙酯水解表现出相当强的抑制活性。对二肽H - 反式δE苯丙氨酸 - 亮氨酸（或苯丙氨酸） - 甲酯（或羟基）抑制作用的动力学分析表明，其抑制模式为竞争性。对抑制常数Ki的比较分析阐明了引发抑制活性所需的几个结构要素。这些要素包括反式δE苯丙氨酸残基的(2R,3S)构型、2位的苯基侧链以及C末端甲酯化。这些结构条件表明这些肽处于特定的抑制构象。通过高分辨率1H - NMR（270 MHz）对这些二肽抑制剂进行构象分析时，核Overhauser效应增强的测量表明，反式δ苯丙氨酸 - 苯基与酯 - 甲基之间存在分子内疏水键，从而在分子中构建了疏水核心。有人认为，这个疏水核心与胰凝乳蛋白酶的S2位点相互作用，阻止甲酯的水解。亮氨酸2或苯丙氨酸2与酶的S1位点相互作用。含有2,3-甲桥苯丙氨酸的二肽结构已被表征为一种在其催化中心与酶相互作用的酶抑制构象。
