Abstract

Ethylene diamine tetraacetic acid, magnesium chloride, methylene blue, cysteine and reduced glutathione could not protect mitochondrial DPN-linked dehydrogenases against the inhibitory effects of N , N'-di-secondary butyl dithiooxamide and N , N'-diallyldithiooxamide.

Some protection could be obtained with coenzyme I, however if apoenzyme and inhibitor were preincubated prior to the addition of coenzyme, no reversal of the inhibition was observed.

A study of the comparative affinities of coenzyme I and inhibitor for enzyme site in the alcohol dehydrogenase system showed this relationship to be a comparative one. However, it was dependent upon the order of addition of reactants and other factors.

The potent substituted dithiooxamides are chelating agents having an affinity for certain divalent metals, including zinc. The requirements for optimum chelating activity are discussed. Factors which influence the rate of chelate formation also influence the degree of inhibition of alcohol dehydrogenase by these agents.

Both the forward and backward reactions of the alcohol dehydrogenase system are depressed by small amounts of the inhibitor. The lactic to pyruvic step of the lactic dehydrogenase system is affected, the backward reaction is insensitive.

These compounds do not inhibit glucose-6-phosphate dehydrogenase, a coenzyme II(TPN)-linked spoenzyme. Glycolysis is likewise unaffected.

The effect of N , N'-di-secondary butyl dithiooxamide and its zinc chelate in producing toxicity in vivo is compared.

The relationship between inhibition of zinc-containing dehydrogenases by these agents and their toxicity is discussed.