Effect of Ethylenediamine Tetracetic Acid, Magnesium and Calcium on Succinate and Keto Acid Metabolism.

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Abstract
Ethylenediamine tetracetic acid (EDTA) causes an increased accumulation of oxaloacetic acid (OAA) during succinate oxidation. DPN is required for this effect. Mg++, Mn++ or Ca++ reverses this a action, the former 2 ions by stimulating utilization of OAA, the latter by accelerating the destruction of the coenzyme (thus decreasing the formation of OAA). Succinate oxidation is inhibited by EDTA only when this agent simultaneously causes an increase in keto acid accumulation. EDTA also increases the rate of OAA utilization apparently by upsetting the Mg++ - Ca++ ratio in the cell. The former ion stimulates OAA utilization, the latter inhibits it and both metals evidently compete for an active site on an enzyme or enzyme-substrate complex. Mg++ apparently forms an unstable complex with OAA which is no longer inhibitory to succinic dehydrogenase.