Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, Montana 59812, United States.
Department of Chemistry and Biochemistry, Washington State University, Pullman, Washington 99164, United States.
Chem Res Toxicol. 2020 Sep 21;33(9):2455-2466. doi: 10.1021/acs.chemrestox.0c00236. Epub 2020 Sep 9.
Studies with acetylcholinesterase (AChE) inhibited by organophosphorus (OP) compounds with two chiral centers can serve as models or surrogates for understanding the rate, orientation, and postinhibitory mechanisms by the nerve agent soman that possesses dual phosphorus and carbon chiral centers. In the current approach, stereoisomers of -methyl, [-(succinic acid, diethyl ester), -(4-nitrophenyl) phosphorothiolate (MSNPs) were synthesized, and the inhibition, reactivation, and aging mechanisms were studied with electric eel AChE (eeAChE) and recombinant mouse brain AChE (rmAChE). The MSNP isomer was the strongest inhibitor of both eeAChE and rmAChE at 8- and 24-fold greater potency, respectively, than the weakest isomer. eeAChE inhibited by the - or -MSNP isomer underwent spontaneous reactivation ∼10- to 20-fold faster than the enzyme inhibited by - and -MSNP, and only 4% spontaneous reactivation was observed from the -eeAChE adduct. Using 2-pyridine aldoxime methiodide (2-PAM) or trimedoxime (TMB-4), eeAChE inhibited by - or -MSNP reactivated up to 90% and 3- to 4-fold faster than eeAChE inhibited by the - or -MSNP isomer. Spontaneous reactivation rates for rmAChE were 1.5- to 10-fold higher following inhibition by - and -MSNPs than inhibition by either isomer, a trend opposite to that found for eeAChE. Oxime reactivation of rmAChE following inhibition by - and -MSNPs was 2.5- to 5-fold faster than inhibition by - or -MSNPs. Due to structural similarities, MSNPs that phosphylate AChE with the loss of the -nitrophenoxy (PNP) group form identical, nonreactivatable adducts to those formed from -isomalathion; however, all the MSNP isomers inhibited AChE to form adducts that reactivated. Thus, MSNPs inactivate AChE via the ejection of either PNP or thiosuccinyl groups to form a combination of reactivatable and nonreactivatable adducts, and this differs from the mechanism of AChE inhibition by isomalathion.
具有两个手性中心的有机磷（OP）化合物抑制的乙酰胆碱酯酶（AChE）研究可以作为理解具有双重磷和碳手性中心的神经毒剂沙林的速率、取向和抑制后机制的模型或替代物。在当前的方法中，合成了 [（琥珀酸，二乙酯）-（4-硝基苯基）膦硫代酸酯，（MSNPs）的-甲基，[（-异构体，并研究了电鳗 AChE（eeAChE）和重组鼠脑 AChE（rmAChE）的抑制、重活化和老化机制。MSNP 异构体对 eeAChE 和 rmAChE 的抑制作用分别比最弱的异构体强 8 倍和 24 倍，是最强的抑制剂。与由 -和 -MSNP 抑制的酶相比，受 -或 -MSNP 异构体抑制的 eeAChE 自发重活化快 10-20 倍，并且仅观察到 -eeAChE 加合物的 4%自发重活化。使用 2-吡啶醛肟甲碘化物（2-PAM）或三甲氧基肟（TMB-4），与由 -或 -MSNP 抑制的 eeAChE 相比， -或 -MSNP 抑制的 eeAChE 的重活化率提高了 90%和 3-4 倍。与 eeAChE 相反，rmAChE 受到 -和 -MSNPs 抑制后的自发重活化率比受任何 -MSNP 异构体抑制后的重活化率高 1.5-10 倍。rmAChE 受到 -和 -MSNPs 抑制后的肟重活化速度比受到 -或 -MSNPs 抑制后的速度快 2.5-5 倍。由于结构相似，使 AChE 失磷失去-硝基苯氧基（PNP）基团的 MSNPs 形成与从 -异马拉硫磷形成的相同的、不可重活化的加合物；然而，所有的 MSNP 异构体都抑制 AChE 形成可重活化的加合物。因此，MSNPs 通过排出 PNP 或琥珀酰基基团使 AChE 失活，形成可重活化和不可重活化的加合物的组合，这与异马拉硫磷抑制 AChE 的机制不同。
