The G-type nerve agents, sarin (GB), soman (GD), and cyclosarin (GF), are among the most toxic compounds known. Much progress has been made in evolving the enzyme phosphotriesterase (PTE) from Pseudomonas diminuta for the decontamination of the G-agents; however, the extreme toxicity of the G-agents makes the use of substrate analogues necessary. Typical analogues utilize a chromogenic leaving group to facilitate high-throughput screening, and substitution of an O-methyl for the P-methyl group found in the G-agents, in an effort to reduce toxicity. Till date, there has been no systematic evaluation of the effects of these substitutions on catalytic activity, and the presumed reduction in toxicity has not been tested. A series of 21 G-agent analogues, including all combinations of O-methyl, p-nitrophenyl, and thiophosphate substitutions, have been synthesized and evaluated for their ability to unveil the stereoselectivity and catalytic activity of PTE variants against the authentic G-type nerve agents. The potential toxicity of these analogues was evaluated by measuring the rate of inactivation of acetylcholinesterase (AChE). All of the substitutions reduced inactivation of AChE by more than 100-fold, with the most effective being the thiophosphate analogues, which reduced the rate of inactivation by about 4–5 orders of magnitude. The analogues were found to reliably predict changes in catalytic activity and stereoselectivity of the PTE variants and led to the identification of the BHR-30 variant, which has no apparent stereoselectivity against GD and a k_cat/K_m of 1.4 × 10⁶, making it the most efficient enzyme for GD decontamination reported till date.

中文翻译：

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用于有机磷神经毒剂——沙林、索曼和环沙林的酶催化解毒的底物类似物

G 型神经毒剂、沙林 (GB)、索曼 (GD) 和环沙林 (GF) 是已知毒性最强的化合物之一。在从Pseudomonas diminuta进化出磷酸三酯酶 (PTE)以净化 G 剂方面取得了很大进展；然而，G 剂的极端毒性使得必须使用底物类似物。典型的类似物利用显色离去基团来促进高通量筛选，并用O-甲基取代P-甲基在 G 剂中发现，以降低毒性。迄今为止，还没有对这些取代对催化活性的影响进行系统评估，并且尚未测试假定的毒性降低。一系列 21 种 G 剂类似物，包括O-甲基、p的所有组合-硝基苯基和硫代磷酸盐取代物已被合成并评估了它们揭示 PTE 变体对真正 G 型神经毒剂的立体选择性和催化活性的能力。通过测量乙酰胆碱酯酶 (AChE) 的失活率来评估这些类似物的潜在毒性。所有的取代都将 AChE 的失活降低了 100 倍以上，其中最有效的是硫代磷酸盐类似物，它将失活率降低了约 4-5 个数量级。发现类似物可以可靠地预测 PTE 变体的催化活性和立体选择性的变化，并导致 BHR-30 变体的鉴定，该变体对 GD 和k _cat / K没有明显的立体选择性_m为 1.4 × 10 ⁶，使其成为迄今为止报道的最有效的 GD 去污酶。