The effect of s-triazine-type pesticides and chlorinated hydrocarbons on lactate dehydrogenase

The effect of pesticides on nontarget organisms was studied by following their effect on enzymes from these organisms in vitro. s-Triazines substituted in positions 2, 4, and 6 behaved as inhibitors of plant and animal lactate dehydrogenase, acting competitively with respect to the coenzyme. The inhibition constants were of the order of 10(-3) M and the structure of the substituents exerted no pronounced effect on the inhibition type and the value of the inhibition constant. Polycyclic chlorinated hydrocarbons were found to be much stronger inhibitors, with inhibition constants of the order of 10(-5) M. These substances inhibit the reaction catalyzed by lactate dehydrogenase not only by reaction with the enzyme, but also by a probable direct reaction with the coenzyme.