Inhibition of human glutathione transferases by pesticides: Development of a simple analytical assay for the quantification of pesticides in water

Glutathione transferases (GSTs; EC 2.5.1.18) form a group of multifunctional enzymes that are involved in phase II cellular detoxification mechanism. Here, screening of the inhibition potency of a wide range of pesticides toward selected human GST isoenzymes (hGSTA1-1, hGSTP1-1, hGSTT2-2 and hGSTO1-1) was carried out. hGSTA1-1 was found more susceptible to inhibition by pesticides than other isoenzymes. The insecticides dieldrin and spiromesifen were identified as potent reversible inhibitors toward hGSTA1-1 with IC50 values equal to 17.9 ± 1.7 μM and 12.1 ± 3.4 μM, respectively. Based on in silico docking analysis and kinetic inhibition studies it was concluded that dieldrin and spiromesifen bind specifically to the enzyme presumably at a distinct position that partially overlaps with both the G- and H-site. The ability of dieldrin and spiromesifen to inhibit hGSTA1-1 activity was exploited for the development of analytical quantification assays for these two pesticides. Linear calibration curves were obtained for dieldrin and spiromesifen, with useful concentration in the range of 0–10 μM. The reproducibility of the assay response, expressed by relative standard deviation, was in the order of 4.1% (N = 28). The method was successfully applied to the determination of these pesticides in real water samples without sample preparation steps.

The insecticides dieldrin and spiromesifen were identified as potent reversible inhibitors toward hGSTA1-1. Based on in silico docking analysis and kinetic inhibition studies it was concluded that dieldrin and spiromesifen bind specifically to the enzyme presumably at a distinct position that partially overlaps the substrates binding site. The ability of dieldrin and spiromesifen to inhibit hGSTA1-1 activity was exploited for the development of analytical quantification assays for these two pesticides. The reproducibility of the assay response, expressed by relative standard deviation (RSD), was in the order of 4.1% (N = 28). The method was successfully applied to the determination of these pesticides in real water samples without sample preparation steps. The proposed assay offers clear and distinct advantages, such as low cost, real-time detection with minimum sample preparation and sample handling, over standard analytical methods for the direct monitoring of dieldrin and spiromesifen.Figure optionsDownload as PowerPoint slideHighlights
► The ability of dieldrin and spiromesifen to inhibit hGSTA1-1 was exploited.
► Analytical assays for dieldrin and spiromesifen were developed.
► The reproducibility, expressed by RSD, was in the order of 4.1% (N = 28).
► Determination of pesticides in water without sample preparation steps was achieved.