Biocatalytic Buffering System for Detoxification of Nerve Agents

摘要

A major obstacle in the utility of enzymes for decontamination purposes is their sensitivity to their surrounding environment. Enzymes are only catalytically active within a narrow range of conditions including pH and temperature. Sensitivity to pH is of particular importance in hydrolysis reactions due to the generation of acidic products. In the enzymatic hydrolysis of nerve agents, to prevent inaction of the enzyme prior to complete conversion of the toxin, tight control of pH over the full time course of detoxification is required. To counter this sensitivity, we have developed a method of controlling pH during enzyme-mediated detoxification by using the urease- catalyzed hydrolysis of urea. Base generated by urea hydrolysis neutralizes the formation of acid such that a dynamic pH equilibrium is created between the competing reactions. We have successfully demonstrated the use of biocataltyic pH control in the detoxification of both paraoxon and DFP by OPH. Results indicated that urease from jack bean and Helicobacter pylori were significantly inhibited by fluoride, a product DFP hydrolysis, at concentrations in the micromolar range. Means of overcoming this inhibition including the use of fluoride scavengers and alternative base-producing enzymatic reactions was studied.