Delineation and Decomposition of Energies Involved in Quaternary Ammonium Binding in the Active Site of Acetylcholinesterase
作者:Daniel M. Quinn、Shawn R. Feaster、Haridasan K. Nair、Nathan A. Baker、Zoran Radić、Palmer Taylor
DOI:10.1021/ja9933588
日期:2000.4.1
quaternary ammonium binding locus in the active site of mammalian acetylcholinesterase is subtended by the side chains of Trp86, Tyr133, Glu202, and Tyr337. Linear free-energy relationships define the interactions involved in molecular recognition by mouse acetylcholinesterase of the quaternary ammonium moiety of ligands. For substrates CH3C(O)XCH2CH2Y [X = O, Y = CHMe2, or CH2CH3; X = S, Y = H, NH+Me2
哺乳动物乙酰胆碱酯酶活性位点中的季铵结合位点由 Trp86、Tyr133、Glu202 和 Tyr337 的侧链包覆。线性自由能关系定义了小鼠乙酰胆碱酯酶对配体季铵部分的分子识别所涉及的相互作用。对于底物 CH3C(O)XCH2CH2Y [X = O, Y = CHMe2, 或 CH2CH3; X = S、Y = H、NH+Me2 或 N+Me3 ] 和三氟苯乙酮过渡态类似物抑制剂 m-YC6H4C(O)CF3 [Y = H、Me、Et、iPr、tBu、CF3、NH2、NO2、NMe2 ,或 N+Me3]、log(kcat/Km) 和 pKi 与取代基 Y 的摩尔折射率呈线性关系,但与疏水性无关。这些相关性表明,在催化的酰化阶段,季铵结合位点中的相互作用使四面体中间体(由过渡态类似物亲和力建模)稳定(5 × 105)倍(ΔΔGTI = -32.5 kJ mol-1)和过渡态稳定(2 × 104)倍(ΔΔG‡