The effect of potentially toxic elements and sewage sludge on the activity of regulatory enzyme glutamate kinase

The glutamate kinase activity was investigated as a plant stress response to Cd, Zn, As or sewage sludge application to soil in the pot and field experiments with spinach (Spinacia oleracea L.). Allosteric regulation of glutamate kinase activity by free proline creates a possibility for an increase in glutamic acid content due to the synthesis of glutathione and phytochelatines in plant cells. For this reason the high rates of As, Cd and Zn applied into soil strongly decreased the glutamate kinase activity. Allosteric regulation of the glutamate kinase activity did not inhibit the synthesis of proline and hydroxyproline under stress condition caused by organic pollutants after application of sewage sludge. Formed proline was bound to stress proteins and therefore glutamate kinase activity was not inhibited.