Département de Toxicologie, Institut de Recherches Biomédicales des Armées, 38700 La Tronche, France.
Toxicol Lett. 2011 Sep 25;206(1):14-23. doi: 10.1016/j.toxlet.2011.05.1041. Epub 2011 Jun 12.
Bioscavengers are molecules able to neutralize neurotoxic organophosphorus compounds (OP) before they can reach their biological target. Human butyrylcholinesterase (hBChE) is a natural bioscavenger each molecule of enzyme neutralizing one molecule of OP. The amount of natural enzyme is insufficient to achieve good protection. Thus, different strategies have been envisioned. The most straightforward consists in injecting a large dose of highly purified natural hBChE to increase the amount of bioscavenger in the bloodstream. This proved to be successful for protection against lethal doses of soman and VX but remains expensive. An improved strategy is to regenerate prophylactic cholinesterases (ChE) by administration of reactivators after exposure. But broad-spectrum efficient reactivators are still lacking, especially for inhibited hBChE. Cholinesterase mutants capable of reactivating spontaneously are another option. The G117H hBChE mutant has been a prototype. We present here the Y124H/Y72D mutant of human acetylcholinesterase; its spontaneous reactivation rate after V-agent inhibition is increased up to 110 fold. Catalytic bioscavengers, enzymes capable of hydrolyzing OP, present the best alternative. Mesophilic bacterial phosphotriesterase (PTE) is a candidate with good catalytic efficiency. Its enantioselectivity has been enhanced against the most potent OP isomers by rational design. We show that PEGylation of this enzyme improves its mean residence time in the rat blood stream 24-fold and its bioavailability 120-fold. Immunogenic issues remain to be solved. Human paraoxonase 1 (hPON1) is another promising candidate. However, its main drawback is that its phosphotriesterase activity is highly dependent on its environment. Recent progress has been made using a mammalian chimera of PON1, but we provide here additional data showing that this chimera is biochemically different from hPON1. Besides, the chimera is expected to suffer from immunogenic issues. Thus, we stress that interest for hPON1 must not fade away, and in particular, the 3D structure of the hPON1 eventually in complex with OP has to be solved.
生物清除剂是能够在神经毒性有机磷化合物 (OP) 到达其生物靶标之前将其中和的分子。人丁酰胆碱酯酶 (hBChE) 是一种天然的生物清除剂，每个酶分子可中和一个 OP 分子。天然酶的数量不足以达到良好的保护效果。因此，已经设想了不同的策略。最简单的方法是注射大量高度纯化的天然 hBChE，以增加血液中生物清除剂的数量。这已被证明对保护免受梭曼和 VX 的致死剂量有效，但仍然昂贵。一种改进的策略是在用 OP 抑制剂处理后通过给予再活化剂来再生预防性胆碱酯酶 (ChE)。但仍缺乏广谱高效的再活化剂，尤其是对抑制的 hBChE。能够自发再活化的胆碱酯酶突变体是另一种选择。G117H hBChE 突变体就是一个原型。我们在这里介绍人类乙酰胆碱酯酶的 Y124H/Y72D 突变体；其在 V 型剂抑制后的自发再活化速率提高了 110 倍。能够水解 OP 的酶类即催化生物清除剂是最佳选择。嗜温细菌磷酸三酯酶 (PTE) 是一种具有良好催化效率的候选物。通过合理设计，其对最有效的 OP 异构体的对映选择性得到了增强。我们表明，该酶的聚乙二醇化使其在大鼠血液中的平均停留时间延长了 24 倍，生物利用度提高了 120 倍。免疫原性问题仍有待解决。人对氧磷酶 1 (hPON1) 是另一个有前途的候选物。然而，其主要缺点是其磷酸三酯酶活性高度依赖于其环境。使用 PON1 的哺乳动物嵌合体取得了一些进展，但我们在这里提供了额外的数据，表明该嵌合体在生化上与 hPON1 不同。此外，该嵌合体预计会引起免疫原性问题。因此，我们强调，对 hPON1 的兴趣不能减弱，特别是要解决 hPON1 最终与 OP 形成复合物的三维结构。
