Hallek M, Szinicz L
Institut für Pharmakologie und Toxikologie, Akademie des Sanitäts- und Gesundheitswesens der Bundeswehr, Garching-Hochbrück, Federal Republic of Germany.
Biochem Pharmacol. 1988 Mar 1;37(5):819-25. doi: 10.1016/0006-2952(88)90167-0.
Acetylcholinesterase (AChE) inhibited by the organophosphate soman (1,2,2-trimethyl-propylmethylphosphonofluoridate) rapidly becomes resistant to reactivation by oximes due to dealkylation of the soman-enzyme complex. This reaction is called aging. The effect of the four mono- and bisquaternary ammonium compounds tetramethylammonium (TMA), hexamethonium, decamethonium and suxamethonium on the reactivatability of soman-inhibited, solubilized AChE from human erythrocytes was investigated in vitro. All compounds were reversible inhibitors of AChE; the respective dissociation constants and the type of inhibition exhibited considerable differences. The affinities to both the active and the allosteric site were considerably higher for suxamethonium (Kii 81.3 microM; Ki 15.9 microM) and decamethonium (Kii 15.4 microM; Ki 4.4 microM) than for TMA (Kii 1 mM; Ki 289.6 microM) and hexamethonium (Kii 4.5 mM; Ki 331.8 microM). The reactivation experiments were performed in a four-step procedure (soman-inhibition at 0 degree and pH 10, aging at 37 degrees and pH 7.3, reactivation by the oxime HI 6 at 37 degrees and pH 7.3 followed by AChE assay). After these four steps (total duration 55 min), AChE was inhibited by soman to 95-100%. HI 6 could reactivate about 20% of the inhibited enzyme. All effectors increased the AChE reactivatability by HI 6 when added before aging was started. The maximal increase in reactivatability was higher in the presence of 1.6 mM suxamethonium (+35.8%) and 150 microM decamethonium (+40%) than of 22 mM TMA (+22.5%) and 8.3 mM hexamethonium (+19.2%). If the effectors were added after 5 min of aging they increased the activity of soman-inhibited AChE, but to a considerably smaller extent than HI 6. A good correlation of the respective Kii values and the effective concentrations of these drugs was observed, indicating that an allosteric binding site of AChE might be involved in the protective effect of these drugs.
有机磷酸酯梭曼（1,2,2 - 三甲基丙基甲基磷酰氟）抑制的乙酰胆碱酯酶（AChE）会由于梭曼 - 酶复合物的脱烷基作用而迅速变得对肟类的再活化具有抗性。此反应称为老化。在体外研究了四种单季铵盐和双季铵盐化合物四甲基铵（TMA）、六甲铵、十甲铵和琥珀胆碱对人红细胞中梭曼抑制的、可溶的AChE再活化能力的影响。所有化合物都是AChE的可逆抑制剂；各自的解离常数和抑制类型表现出相当大的差异。琥珀胆碱（Kii 81.3 microM；Ki 15.9 microM）和十甲铵（Kii 15.4 microM；Ki 4.4 microM）对活性位点和变构位点的亲和力比TMA（Kii 1 mM；Ki 289.6 microM）和六甲铵（Kii 4.5 mM；Ki 331.8 microM）高得多。再活化实验按四步进行（在0℃和pH 10下用梭曼抑制，在37℃和pH 7.3下老化，在37℃和pH 7.3下用肟HI 6再活化，随后进行AChE测定）。经过这四个步骤（总时长55分钟）后，AChE被梭曼抑制至95 - 100%。HI 6可使约20%的被抑制酶再活化。在开始老化之前加入时，所有效应物都能提高HI 6对AChE的再活化能力。在存在1.6 mM琥珀胆碱（+35.8%）和150 microM十甲铵（+40%）时，再活化能力的最大增幅高于22 mM TMA（+22.5%）和8.3 mM六甲铵（+19.2%）。如果在老化5分钟后加入效应物，它们会增加梭曼抑制的AChE的活性，但增幅远小于HI 6。观察到各自的Kii值与这些药物的有效浓度之间有良好的相关性，表明AChE的一个变构结合位点可能参与了这些药物的保护作用。
