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Organophosphorus acid anhydrolase (OPAA) is an enzyme that been shown to be particularly effective in detoxifying organophosphorus-containing compounds, such as deadly nerve gas used in chemical warfare.〔Hoskin, F. C. G., and A. H. Rousch. 1982. Hydrolysis of nerve gas by squid type diisopropylphosphorofluoridate hydrolyzing enzyme on agarose resin. Science 215:1255-1257.〕 The enzyme is found in a diverse range of organisms, including protozoa,〔Landis, W. G., H. D. Durst, R. E. Savage, Jr., D. M. Haley, M. V. Haley, and D. W. Johnson. 1987. Discovery of multiple organofluorophosphate hydrolyzing activities in the protozoan Tetrahymena thermophila. J. Appl. Toxicol. 7:35-41.〕 squid and clams,〔Anderson, R. S., H. D. Durst, and W. G. Landis. 1988. Initial characterization of the organophosphate acid anhydrase activity in the clam, Rangia cuneata. Comp. Biochem. Physiol. 91C: 575-578.〕 mammals,〔Little, J. S., C. A. Broomfield, L. J. Boucher, and M. K. Fox-Talbot. 1986. Partial characterization of a rat liver enzyme that hydrolyzes sarin, soman, tabun and DFP. Fed. Proc. 45:791.〕 and soil bacteria.〔DeFrank, J. J., and T.-C. Cheng. 1991. Purification and properties of an organophosphorus acid anhydrase from a halophilic bacterial isolate. J. Bacteriol. 173:1938-1943.〕 A highly active form of the enzyme is typically isolated from the marine bacteria ''Alteromonas undina'' for laboratory study.〔Cheng, T., Harvey, S., & Stroup, A. (1993). Purification and properties of a highly active organophosphorus acid anhydrolase from alteromonas undina. Applied Environmental Microbiology, 59(9), 3138-3140. Retrieved from http://aem.asm.org/content/59/9/3138.short〕 This form is both halophilic and thermophilic, making it particularly useful for detoxification applications. A slightly less active variant of OPAA has also been isolated in mung beans and slime mold duckweed.〔Hoskin, F., Walker, J., & Mello, C. (1999). Organophosphorus acid anhydrolase in slime mold duckweed and mung bean: a continuing search for a physiological role and a natural substrate. Chemico-Biological Interactions, 119-120, 399-404. Retrieved from http://dx.doi.org/10.1016/S0009-2797(99)00051-4〕 ==Enzyme mechanism== Although the exact mechanism of OPAA’s nerve-agent detoxification is unclear, researchers have deduced that the basic reaction follows a general base mechanism with a simple in-line displacement of fluoride at the phosphorus center using an activated water molecule, as seen in Figure 1.〔Dumas, DP, Caldwell, SR, Wild, JR, and Raushel, FM, Purification and Properties of the Phosphotriesterase from Pseudomonas diminuta, Journal Biological Chemistry, 264 (1989) 19659-19665.〕 OPAA activity is enhanced by reducing agents such as dithiothreitol (DTT) and beta-mercaptoethanol.〔Elashvili, I, DeFrank, JJ, and Culotta, VC, Purification and characterization of DFPase from Alteromonas haloplanktis ATCC 14393, Proceedings of the 1998 ERDEC Scientific Conference on Chemical and Biological Defense Research, 17–20 November 1998, AD-A375 171.〕 OPAA is also catalytically active over a wide pH range between 6.5 and 9.5 and temperature range between 10 and 65 °C, and is stimulated by manganese.〔Lewis, VE, Donarski, WJ, Wild, JR, and Raushel, FM, Mechanism and Stereochemical course at phosphorus of the reaction catalyzed by a bacterial phosphotriesterase, Biochemistry 27 (1988) 1591-1597.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Organophosphorus acid anhydrolase」の詳細全文を読む スポンサード リンク
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