The purification, characterization, and inhibition profile of some herbicides of glutathione S-transferase from broccoli

Herbicide selectivity is determined by the variability of herbicide degradation processes in weeds and crops. Glutathione S-transferases (GSTs) have been widely studied in plants because of their role in herbicide metabolism. GSTs metabolize herbicides by catalyzing reduced glutathione (GSH) conjugation. The significance of GSTs in herbicide metabolism has been understood by examining GST in some plants. In this study, a GST enzyme was purified from broccoli using an affinity chromatography (glutathione agarose) method to contribute to the elucidation of plant GSTs. A characterization of the purified broccoli GST enzyme was then carried out. In the last step, the inhibition profiles of some selected types of herbicides on the activity of the broccoli GST enzyme were studied. In the purification studies conducted as part of the study, the GST enzyme was purified 101.34-fold with a yield of 18.84% from broccoli. The optimal conditions (temperature, pH, ionic strength) of broccoli GST were found to be 60 degrees C, 7.5, and 1.25 M, respectively. The KM constants of broccoli GST were determined to be 0.465 and 2.355 mM for its two substrates, 1-chloro-2,4-dinitrobenzene and GSH, respectively, and the V max for the same two substrates was determined to be 0.251 and 0.424 EU/mL, respectively. SDS-PAGE was used to check the purity of the enzyme, and it was determined to have a molecular weight in the range of 35-40 kDa. Inhibition studies were also conducted to determine the inhibitory effects of the herbicides pendimethalin, bentazone, and glyphosate. The IC50 values were determined to be 173.25, 0.438, and 0.536 mu M for pendimethalin, bentazone, and glyphosate, respectively. The best inhibitor of the GST enzyme was found to be bentazone, with the lowest Ki value of 0.318 +/- 0.079 mu M.