Thomas T C, Székács A, Rojas S, Hammock B D, Wilson B W, McNamee M G
Department of Biochemistry and Biophysics, University of California, Davis 95616.
Biochem Pharmacol. 1990 Dec 15;40(12):2587-96. doi: 10.1016/0006-2952(90)90575-6.
Neuropathy target esterase (NTE) is a membrane-bound carboxylesterase activity which is proposed as the target site in nerve tissue for initiation of organophosphate-induced delayed neuropathy. This activity is identified as phenyl valerate hydrolysis which is resistant to treatment with paraxon and sensitive to co-incubation with paraxon and mipafox. NTE preparations were obtained, which did not contain paraxon-sensitive or mipafox-resistant hydrolases, by selective reconstitution of detergent-solubilized NTE from chick embryo brain into asolectin vesicles during gel filtration. The topography of the catalytic site of NTE was then examined by investigating the inhibition of NTE by a series of 3-alkylthio- and 3-arylthio-1,1.1-trifluoro-propan-2-ones. These trifluoromethyl ketones were found to be rapidly reversible, competitive inhibitors of NTE with I50 values 1.3 x 10(-4) M to 4.9 x 10(-8) M. Correlation of I50 values with octanol/water partition coefficients (P), in the range of log P = 1.5 to 5.9. indicated that the optimal lipophilicity for NTE substrates and inhibitors is in the range of log P = 3.0 to 3.4. Electrophilic substitution at the meta position of aromatic rings increased the inhibitory capacity of these inhibitors, whereas substitution at the ortho position reduced inhibitory capacity. These results indicate both that a large hydrophobic pocket is closely associated with the catalytic residue of NTE, and that affinity for the active site is affected by steric and electronic parameters.
神经病变靶酯酶（NTE）是一种膜结合的羧酸酯酶活性，被认为是神经组织中有机磷酸酯诱导的迟发性神经病变起始的靶位点。这种活性被鉴定为对氧磷处理具有抗性且对与对氧磷和丙胺氟磷共同孵育敏感的戊酸苯酯水解。通过在凝胶过滤过程中将来自鸡胚脑的去污剂增溶的NTE选择性重构到大豆卵磷脂囊泡中，获得了不含对氧磷敏感或丙胺氟磷抗性水解酶的NTE制剂。然后通过研究一系列3-烷硫基和3-芳硫基-1,1,1-三氟-2-丙酮对NTE的抑制作用，来检查NTE催化位点的拓扑结构。发现这些三氟甲基酮是NTE的快速可逆竞争性抑制剂，I50值在1.3×10⁻⁴M至4.9×10⁻⁸M范围内。I50值与辛醇/水分配系数（P）在log P = 1.5至5.9范围内的相关性表明，NTE底物和抑制剂的最佳亲脂性在log P = 3.0至3.4范围内。芳环间位的亲电取代增加了这些抑制剂的抑制能力，而邻位取代则降低了抑制能力。这些结果表明，一个大的疏水口袋与NTE的催化残基紧密相关，并且对活性位点的亲和力受空间和电子参数的影响。
