Biological synthesis of oxaloacetic acid from pyruvic acid and carbon dioxide

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Abstract
Suspensions of minced pigeon liver form the same substances from added pyruvate and from added oxaloacetate, viz. [alpha]-ketoglutarate, fumarate, malate, succinate and citrate. Various explanations are discussed; the only satisfactory one assumes that oxaloacetate forms from pyruvate and CO2 (reaction I). The rate of pyruvate usage in pigeon liver depends on the cones, of CO2 and bicarbonate, as expected by reaction I. The rate of pyruvate usage of liver suspension from vit. B1-deficient pigeons is greatly reduced; the normal rate is restored by the addition of pure vit. B1. Under the same conditions pyruvate usage in muscle suspensions, i.e., pyruvate usage through the citric acid cycle, is not increased by the vit. The vit. takes part in a reaction present in liver, but absent from muscle; hence the conclusion is reached that the vit. catalyses reaction I, the "carboxylation" of pyruvate. It is not excluded that in addition the vit. takes part in the synthesis of acetoacetate from pyruvate. In B. coli fumarate and malate are formed (together with succinate) when pyruvate is anaerobically fermented; this supports the view of Wood and Werkman, that reaction I occurs in bacteria. The CO2 fixation and the equivalence between CO2 fixation and succinate formation in propionic acid bacteria (Wood and Werkman), and the effect of CO2 on the succinate formation in B. coli (Elsden) are satisfactorily explained by this assumption.