Collect. Czech. Chem. Commun. 1986, 51, 1781-1788

Mechanism of action of heavy metals, S-triazine herbicides and nitrates on alcohol dehydrogenase from rape

Marie Stiborová and Sylva Leblová

Department of Biochemistry, Charles University, 128 40 Prague 2


Heavy metals (Pb2+, Cu2+, Cd2+, and Zn2+) inhibited alcohol dehydrogenase (ADH) of rape (EC; Pb2+ and Cd2+ ions affected the imidazole ring of histidine, Cu2+ and Zn2+ ions interacted with the sulphydryl groups of cysteine in the molecule of the enzyme. The coenzyme protected ADH from inactivation by Pb2+ and Cd2+, but did not protect it from Cu2+ and Zn2+. Ethanol in a ternary complex ADH-NAD+ -ethanol was a strong protecting agent from Pb2+ and Cd2+ ions. Nitrates inhibited rape ADH toward any substrate. Sulphates and fluorides had no effect. The S-triazine herbicides studied proved strong inhibitors of rape ADH (their Ki's corresponded to concentrations of the order 10-4 mol 1-1), occupying the binding site for the coenzyme. The herbicides interacted with the metallic component of the enzyme, to which the nicotinamide part of the coenzyme is bound.