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United States Department of Agriculture

Agricultural Research Service


item Gopal, Sriram
item Rastogi, Vipin
item Ashman, William
item Mulbry, Walter

Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Recent U.S. ratification of Chemical Weapons Convention (CWC) has focused public attention on international efforts aimed at the destruction of chemical weapons and the remediation of sites contaminated with these compounds. The destruction of chemical warfare agents and remediation of sites contaminated with these compounds will be an enormously costly process in the U.S. and internationally. Recent progress in the biodegradation of some of these compounds suggests that biological treatment may prove to be the most environmentally and economically feasible strategy for destroying some of the agents and for site remediation. In this research, scientists modified the gene for the bacterial enzyme OPH with the goal of increasing the enzyme's relative activity toward the nerve agent VX. They then tested the modified enzymes against VX and five other related chemicals. Although most of the altered enzymes showed decreased activity toward VX and related compounds, one altered enzyme displayed a 33% increase in the rate of VX destruction. The gene for this better enzyme will be used in further rounds of modification. In addition to using these enzymes for environmental clean-up, the U.S. Army hopes to use such altered enzymes in protective foams and decontaminating agents for soldiers and equipment.

Technical Abstract: Organophosphorus hydrolase (OPH) is capable of hydrolyzing a wide variety of organophosphorus pesticides and chemical warfare agents. However, the hydrolytic activity of OPH against the warfare agent VX is less than 0.1% relative to its activity against parathion and paraoxon. Based on the crystal structure of OPH and the similarities it shares with acetylcholinesterase, eight OPH mutants were constructed with the goal of increasing OPH activity toward VX. The activities of crude extracts from these mutants were measured using VX, demeton-S methyl, diisopropylfluoro-phosphate, ethyl parathion, paraoxon, and EPN as substrates. One mutant (L136Y) displayed a 33% increase in the relative VX hydrolysis rate compared to wild type enzyme. The other seven mutations resulted in 55-76% decreases in the relative rates of VX hydrolysis. There was no apparent relationship between the hydrolysis rates of VX and any the rates of the other organophosphorus compounds tested.

Last Modified: 06/21/2017
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