Conjugation of 2-chloroacetanilide herbicides with glutathione: role of molecular structures and of glutathione S-transferase enzymes
1991
Scarponi, L. | Perucci, P. | Martinetti, L.
The conjugation of acetochlor, alachlor, butachlor, dimethachlor, metolachlor, pretilachlor, and propachlor with glutathione nonenzymatically and enzymatically by action of the glutathione S-transferase (GST) was investigated. Shoots of corn (Zea mays), soybean (Glycine max), wheat (Triticum aestivum), sorghum (Sorghum bicolor), redroot pigweed (Amaranthus retroflexus), and lambsquarter (Chenopodium album) were employed as enzyme sources for enzymatic tests. The nonenzymatic conjugation rates varied to the following order: propachlor > pretilachlor > alachlor > acetochlor > dimethachlor > metolachlor > butachlor. The presence of enzyme extracts induced significant conjugation increases that differed according to the enzyme source. Furthermore, within each enzyme source a different decreasing order of the conjugation rate, compared to the nonenzymatic reaction, was observed. Therefore, interferences of the molecular structure of the 2-chloroacetanilides also in the enzymatic mechanism of the reaction have been deduced. These findings and the kinetic parameters (KM and Vmax), determined for the GST enzymes of each plant, show that the molecular structure of the 2-chloroacetanilides, the catalytic efficiency of GST enzymes, their concentration in the protein bulk, and the protein content in plants are crucial factors in determining plant tolerance.
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