Detoxification of organophosphorus compounds by recombinant carboxylesterase from an insecticide-resistant mosquito and oxime-induced amplification of enzyme activity

Abstract

Currently, bioremediation is a promising approach to the degradation of environmental pollutants. Here we describe the application of the recombinant insecticide-resistant mosquito carboxylesterase B1 to detoxify organophosphorous compounds. However, this approach has a major limitation: 1:1 stoichiometry of the enzyme detoxification of those organophosphorous compounds containing no carboxyl ester bonds, such as paraoxon, chlorpyrifos etc. To improve the effectiveness of the enzymatic detoxification of organophosphorous compounds, we used a combination of carboxylesterase B1 with the uncharged oxime diacetylmonoxime. It was demonstrated that the repeated addition of 20 times the molar concentration of paraoxon to carboxylesterase B1 every 2 h in the presence of 4 mM diacetylmonoxime did not result in significant inhibition of the enzyme. The stoichiometry of enzyme detoxification was higher than 45:1 and 20:1 for paraoxon and chlorpyrifos, respectively. The kinetic experiments on reactivation of organophosphorus compound-inhibited carboxylesterase B1 showed that the half-life for paraoxon- and chlorpyrifos-inhibited carboxylesterase reactivation is 0.75 and 0.88 h, respectively. Using the recombinant insecticide-resistant mosquito carboxylesterase with oxime is an effective approach for detoxification of organophosphorous compounds.