Use of Engineered Enzymes to Identify Organophosphate and Pyrethroid-Related Toxicity in Toxicity Identification Evaluations

Engineered variants of a carboxylesterase from Lucilia cuprina (M) and a phosphotriesterase from Agrobacterium radiobacter (OpdA) with enhanced hydrolytic activities against pyrethroid and organophosphate pesticides were evaluated as a toxicity identification evaluation (TIE) manipulation. Reduction in toxicity in the presence of the enzyme provides an indication that the toxicant is the enzyme's target substrate. Carboxy/esterase E3 variants were evaluated to determine if the enzymes could mitigate toxicity of pyrethroids to the amphipod, Hyalella azteca. Enzymes were able to achieve 12-70-fold reduction in toxicity for. bifenthrin, cyfluthrin, and cypermethrin in water. Only a 2-fold reduction in toxicity was observed with pyrethroid-contaminated sediment though the phosphotriesterase OpdA achieved at least a 35-fold reduction in toxicity from the organophosphate chlorpyrifos in sediment Tests with urban runoff samples and agriculture-affected sediments demonstrated that the enzymes could be useful in TIES to identify pesticide-related toxicity. The approach promises to be a useful TIE tool for organophosphate and pyrethroid pesticides, particularly in a water matrix, and potentially could be used for identification of toxicity attributable to other pesticides.