Olive tree glutathione S-transferase and its response against the herbicides oxyfluorfen and glyphosate

Glutathione S-transferases (GST, EC 2.5.1.18) are a group of detoxifying enzymes that catalyze the conjugation of glutathione to certain toxins or xenobiotics. These enzymes are very well characterized in mammals and plants in general but not in the olive tree. In this work the GST specific activity, kinetic behavior, substrate specificity, and protein expression levels have been determined in the leaves, fruits, stems, and roots of olive tree cv. Picual. The results reveal the presence of GST in all the organs, the leaves and roots are containing the highest activity levels. Substrate specificity and molecular mass of subunits differ between organs. The use of the herbicides oxyfluorfen and glyphosate caused barely significant changes in the kinetic behavior and GST protein-expression levels, in general. Only in the stems of the olive tree treated with glyphosate were greater GST specific activity and protein expression detected. As conclusions, GST has been located and characterized in leaves, fruits, stems and roots of olive tree and the action of this enzyme, implied in the detoxification processes in this species, is lightly affected by the soil application of oxyfluorfen and glyphosate.