Soman hydrolysis

As anhydrides, such compounds are subject to spontaneous hydrolysis, which may contribute to detoxification [160]. Thus, soman hydrolysis at pH 7.5 and 37° occurs with a rate constant of 0.003 - 0.004 min-1 and an activation energy of ca. 55 kJ mol 1 [161]. However, most of the published data refer to enzymatic hydrolysis. Enzymes hydrolyzing P-X anhydride bonds are now known as organophosphorus acid anhydrolases (OPA anhydrolases) classified as EC 3.1.8.2 (also known as diisopropyl-fluorophosphatase, DFPase, tabunase, somanase), an activity related to EC 3.1.8.1 (aryldialkyl-phosphatase, paraoxonase, A-esterase) and formerly classified as EC 3.8.2.1 [64] [65] [69], Much public information on these enzymes can be found in [106],... 

E. Walker, Soman Hydrolysis and Detoxication by a Thermophilic Bacterial Enzyme , in Enzymes Hydrolyzing Organophosphorus Compounds , Eds. E. Reiner, W. N. Aldridge, and F. C. G. Hoskin, Ellis Horwood, Chichester, UK, 1989, p. 53-64. 

Comparison of DFP and Soman Hydrolysis Ratio and Stimulation by Mn2+ for Aquatic Organisms... 

The multiple activities in T. thermophila share some of the characteristics of both the squid-type OPA anhydrase and classical Mazur-type OPA anhydrase found in hog kidney. In crude preparations, the OPA anhydrase activity has the characteristics of the hog kidney OPA anhydrase in that it hydrolyzes soman faster than DFP, is stimulated by Mn2+, and is inhibited by mipafox. Further purification has revealed that the hydrolysis of soman and the stimulation of this hydrolysis by Mn2+ is principally due to the Tt DFPase-4. The Tt DFPase-1, Tt DFPase-2, and Tt DFPase-3 hydrolyze soman and DFP at approximately the same rates and demonstrate only moderate stimulation of soman hydrolysis by Mn2+ and yet are inhibited by mipafox. The Tetrahymena OPA anhydrases fall within a narrow range from 96,000 Da to 67,000 Da. However, this range of molecular weights is larger than that typically ascribed to the Mazur-type enzymes. The Tetrahymena OPA anhydrases can be purified by ammonium sulfate precipitation, like the squid-type OPA anhydrase. 

Hoskin, F.C.G., G. Chettur, S. Mainer, and K.E. Steinmann. 1989. Soman hydrolysis and detoxification by a thermophilic bacterial enzyme. In Enzymes Hydrolyzing Organophosphorus Compounds, E. Reiner, F.C.G. Hoskin, and N.W. Aldridge, Eds. Ellis Horwood, Chichester, U.K., pp. 53-64. 

Yeung, D.T., Smith, J.R., Sweeney, R.E., et ah, 2007. Direct detection of stereospecific soman hydrolysis by wild-type human serum paraoxonase. FEES J. 274, 1183-1191. 

The P-atom in sarin (9.84), soman (9.85), and tabun (9.87) is a stereogen-ic center, allowing for stereoselective enzymatic hydrolysis [162], This aspect has been extensively investigated for soman, which exists as four stereoisomers by virtue of the presence of a second stereogenic center (C-atom). These stereoisomers are usually designated as C(+)P(-), C(-)P(+), C(+)P(+), and C(-)P(-), where C(+/-) refers to the 1,2,2-trimethylpropyl moiety and P(+/ ) to the P-atom. Such a nomenclature may be convenient but has no implication for the absolute configuration. The C(+)P( ) and Cf-)P(-) epimers are the more active toward acetylcholinesterase and, hence, the more toxic ones. In contrast, the C(+)P(+) and C(-)P(+) epimers are preferentially hydrolyzed... 

L. P. A. de Jong, C. van Dijk, H. P. Benschop, Hydrolysis of the Four Stereoisomers of Soman Catalyzed by Liver Homogenate and Plasma from Rat, Guinea Pig and Marmoset and by Human Plasma , Biochem. Pharmacol. 1988, 37, 2939-2948. 

Jenkins AL, Uy OM, Murray GM. Polymer-based lanthanide luminescent sensor for detection of the hydrolysis product of the nerve agent Soman in water. Anal Chem 1999 71 373-378. 

Irreversible cholinesterases are mostly organophosphorus compounds and combine only with esteratic site of cholinesterase and that site gets phosphorylated. The hydrolysis of phosphorylated site produces irreversible inhibition of cholinesterase. And, because, of this property, the therapeutic usefulness is very limited. Most of the compounds are used as insecticides e.g. parathion, malathion and war gases e.g. tabun, sarin, soman etc. 

Menger et al. synthesized a Ci4H29-attached copper(II) complex 3 that possessed a remarkable catalytic activity in the hydrolysis of diphenyl 4-nitrophenyl phosphate (DNP) and the nerve gas Soman (see Scheme 2) [21], When 3 was used in great excess (ca. 1.5 mM, which is more than the critical micelle concentration of 0.18 mM), the hydrolysis of DNP (0.04 mM) was more than 200 times faster than with an equivalent concentration of the nonmicellar homo-logue, the Cu2+-tetramethylethylenediamine complex 9, at 25°C and pH 6 (Scheme 4). The DNP half-life is calculated to be 17 sec with excess 1.5 mM 3 at 25°C and pH 6. The possible reasons for the rate acceleration with 3 were the enhanced electrophilicity of the micellized copper(II) ion or the acidity of the Cu2+-bound water and an intramolecular type of reaction due to the micellar formation. On the basis of the pH(6-8.3)-insensitive rates, Cu2+-OH species 3b (generated with pK3 < 6) was postulated to be an active catalytic species. In this study, the stability constants for 3 and 9 and the thermodynamic pvalue of the Cu2+-bound water for 3a —> 3b + H+ were not measured, probably because of complexity and/or instability of the metal compounds. Therefore, the question remains as to whether or not 3b is the only active species in the reaction solution. Despite the lack of a detailed reaction mechanism, 3 seems to be the best detoxifying reagent documented in the literature. 

P. D Agostino et al., Determination of Sarin, Soman and their hydrolysis products in soil by packed capillary liquid chromatography-electrospray mass spectrometry. J. Chromatogr. A 912, 291-299 (2001)... 

Jenkins et al. produced a fiber optic based luminescence sensor designed to measure a hydrolysis product of the nerve agent soman (GD) in water. The sensor exhibited high selectivity, no interference from organophophorous (OP) herbicides or pesticides, and high sensitivity, with a limit of detection of 600 fg/mL in water (10). 

Using similar LC conditions but employing a sensitive LC/TOF/MS system, the same authors analyzed sarin, soman, and their hydrolysis products in soil (11). Three representative soil types were... 

Cohen, E.M., P.J. Christen, and E. Mobach. 1971. The Inactivation of Oximes of Sarin and Soman in Plasma from Various Species. I. The Influence of Diacetylmonoxime on the Hydrolysis of Sarin. Pp. 113-131 in Proceedings of the Koninklijke Nederlandse Akademie Van Wetenschappen, Series C, Biological and Medical Sciences, Vol. 74. J.A. Cohen Memorial issue. Amsterdam North-Holland. Davies, D.R., P. Holland, and M.J. Rumens. 1960. The relationship between the chemical structure and neurotoxicity of alkyl organophosphorus compounds. Br. J. Pharmacol. 15 271-278... 

Cohen, E.M., P.J. Christen and E. Mobach. 1971. The inactivation by oximes of Sarin and Soman in plasma from various species. I. The influence of diacetylmonoxime on the hydrolysis of Sarin. J.A. Cohen memorial issue. Nordi-Holland Pubhshing Company, Amsterdam. 

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