Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842, USA.
Biochemistry. 2010 Sep 21;49(37):7978-87. doi: 10.1021/bi101056m.
Organophosphorus compounds include many synthetic, neurotoxic substances that are commonly used as insecticides. The toxicity of these compounds is due to their ability to inhibit the enzyme acetylcholine esterase. Some of the most toxic organophosphates have been adapted for use as chemical warfare agents; the most well-known are GA, GB, GD, GF, VX, and VR. All of these compounds contain a chiral phosphorus center, with the S(P) enantiomers being significantly more toxic than the R(P) enantiomers. Phosphotriesterase (PTE) is an enzyme capable of detoxifying these agents, but the stereochemical preference of the wild-type enzyme is for the R(P) enantiomers. A series of enantiomerically pure chiral nerve agent analogues containing the relevant phosphoryl centers found in GB, GD, GF, VX, and VR has been developed. Wild-type and mutant forms of PTE have been tested for their ability to hydrolyze this series of compounds. Mutant forms of PTE with significantly enhanced, as well as relaxed or reversed, stereoselectivity have been identified. A number of variants exhibited dramatically improved kinetic constants for the catalytic hydrolysis of the more toxic S(P) enantiomers. Improvements of up to 3 orders of magnitude relative to the value of the wild-type enzyme were observed. Some of these mutants were tested against racemic mixtures of GB and GD. The kinetic constants obtained with the chiral nerve agent analogues accurately predict the improved activity and stereoselectivity against the authentic nerve agents used in this study.
有机磷化合物包括许多合成的、神经毒性的物质，通常用作杀虫剂。这些化合物的毒性是由于它们能够抑制乙酰胆碱酯酶。一些毒性最强的有机磷化合物已被改编为化学战剂使用；其中最著名的是 GA、GB、GD、GF、VX 和 VR。所有这些化合物都含有一个手性磷中心，S(P)对映体比 R(P)对映体毒性大得多。磷酸三酯酶 (PTE) 是一种能够解毒这些试剂的酶，但野生型酶的立体化学偏好是 R(P)对映体。已经开发出一系列含有 GB、GD、GF、VX 和 VR 中发现的相关磷酰基中心的对映体纯手性神经毒剂类似物。已经测试了野生型和突变型 PTE 水解该系列化合物的能力。已经确定了具有显著增强、松弛或反转立体选择性的 PTE 突变体。一些变体对更有毒的 S(P)对映体的催化水解表现出显著改善的动力学常数。与野生型酶的值相比，观察到高达 3 个数量级的提高。对一些突变体进行了针对 GB 和 GD 外消旋混合物的测试。用手性神经毒剂类似物获得的动力学常数准确地预测了在这项研究中使用的真实神经毒剂的活性和立体选择性的提高。
