1932-60-1Relevant articles and documents
Pathways for the Reactions Between Neurotoxic Organophosphorus Compounds and Oximes or Hydroxamic Acids
Bierwisch, Anne,Koller, Marianne,Worek, Franz,Kubik, Stefan
supporting information, p. 5831 - 5838 (2016/12/18)
To obtain mechanistic insight into the recently demonstrated detoxification ability of β-cyclodextrin derivatives containing substituents with oxime or hydroxamic acid residues, analogous glucose derivatives with the same substituents were treated with cyclosarin (GF), tabun (GA), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) in (Tris)-HCl buffer (0.1 m, pH 7.40), and the different reaction pathways were studied by31P NMR spectroscopy and mass spectrometry. Consistent with previous reports, the oxime is phosphonylated by GF, which is followed by elimination of O-cyclohexyl methylphosphonate to afford a nitrile. Reaction of the hydroxamic acid with GA depends on whether the nitrogen atom of the hydroxamic acid bears a substituent or not. The unsubstituted hydroxamic acid affords a stable phosphate ester lacking the cyanide and the dimethylamino group of GA. If the hydroxamic acid is methylated, the initially formed phosphorylated product undergoes a number of transformations, including cleavage of the C–N bond of the hydroxamic acid. Reaction of the hydroxamic acid with VX involves a Lossen rearrangement. These investigations thus show that all investigated nucleophiles are irreversibly modified upon reaction with nerve agents under the chosen conditions, which indicates that cyclodextrins with oximes or hydroxamic acid as substituents are unlikely to afford catalytic nerve-agent scavengers.
Enzymes for the homeland defense: Optimizing phosphotriesterase for the hydrolysis of organophosphate nerve agents
Tsai, Ping-Chuan,Fox, Nicholas,Bigley, Andrew N.,Harvey, Steven P.,Barondeau, David P.,Raushel, Frank M.
experimental part, p. 6463 - 6475 (2012/10/23)
Phosphotriesterase (PTE) from soil bacteria is known for its ability to catalyze the detoxification of organophosphate pesticides and chemical warfare agents. Most of the organophosphate chemical warfare agents are a mixture of two stereoisomers at the phosphorus center, and the SP-enantiomers are significantly more toxic than the RP-enantiomers. In previous investigations, PTE variants were created through the manipulation of the substrate binding pockets and these mutants were shown to have greater catalytic activities for the detoxification of the more toxic SP-enantiomers of nerve agent analogues for GB, GD, GF, VX, and VR than the less toxic R P-enantiomers. In this investigation, alternate strategies were employed to discover additional PTE variants with significant improvements in catalytic activities relative to that of the wild-type enzyme. Screening and selection techniques were utilized to isolate PTE variants from randomized libraries and site specific modifications. The catalytic activities of these newly identified PTE variants toward the SP-enantiomers of chromophoric analogues of GB, GD, GF, VX, and VR have been improved up to 15000-fold relative to that of the wild-type enzyme. The X-ray crystal structures of the best PTE variants were determined. Characterization of these mutants with the authentic G-type nerve agents has confirmed the expected improvements in catalytic activity against the most toxic enantiomers of GB, GD, and GF. The values of kcat/Km for the H257Y/L303T (YT) mutant for the hydrolysis of GB, GD, and GF were determined to be 2 ×106, 5 ×105, and 8 ×105 M-1 s-1, respectively. The YT mutant is the most proficient enzyme reported thus far for the detoxification of G-type nerve agents. These results support a combinatorial strategy of rational design and directed evolution as a powerful tool for the discovery of more efficient enzymes for the detoxification of organophosphate nerve agents.
Reversed enantioselectivity of diisopropyl fluorophosphatase against organophosphorus nerve agents by rational design
Melzer, Marco,Chen, Julian C.-H.,Heidenreich, Anne,Gaeb, Juergen,Koller, Marianne,Kehe, Kai,Blum, Marc-Michael
supporting information; experimental part, p. 17226 - 17232 (2010/03/25)
Diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris is an efficient and robust biocatalyst for the hydrolysis of a range of highly toxic organophosphorus compounds including the nerve agents sarin, soman, and cyclosarin. In contrast to the substrate diisopropyl fluorophosphate (DFP) the nerve agents possess an asymmetric phosphorus atom, which leads to pairs of enantiomers that display markedly different toxicities. Wild-type DFPase prefers the less toxic stereoisomers of the substrates which leads to slower detoxification despite rapid hydrolysis. Enzyme engineering efforts based on rational design yielded two quadruple enzyme mutants with reversed enantioselectivity and overall enhanced activity against tested nerve agents. The reversed stereochemical preference is explained through modeling studies and the crystal structures of the two mutants. Using the engineered mutants in combination with wild-type DFPase leads to significantly enhanced activity and detoxification, which is especially important for personal decontamination. Our findings may also be of relevance for the structurally related enzyme human paraoxonase (PON), which is of considerable interest as a potential catalytic in vivo scavenger in case of organophosphorus poisoning.
