The Mechanism of the Enzymatic Synthesis of Cocarboxylase*

We have previously shown that the phosphorylation of vitamin B1 to cocarboxylase by an atiozymase preparation is dependent upon the presence of hexosediphosphate and certain heat-stable factors contained in boiled tissue extracts (1). Our results further indicated that this phosphorylation was completely inhibited by 0.0025 to 0.005 M sodium iodoacetate, and that the addition of 0.04 M sodium fluoride had little effect when pyruvic acid was present. We were consequently led to the hypothesis that the phosphorylation of the vitamin occurs either directly or indirectly as a result of a dismutation reaction between triosephosphate and pyruvic acid. Such a dismutation had previously been shown to be effective in the phosphorylation of adenylic acid to adenosine triphosphate by inorganic phosphate (2). According to our view, this same dismutation provides energy for the phosphorylation of the vitamin, though we are unable to state whether the reaction proceeds through adenosine triphosphate or whether it is competitive to the formation of the latter. Sodium fluoride has been shown to inhibit glycolysis by preventing the conversion of phosphoglyceric acid to phosphopyruvic acid (3). In the presence of fluoride then, no pyruvic acid could be formed from hexosediphosphate and, according to our view, the synthesis of cocarboxylase should be inhibited. If sodium pyruvate is added with fluoride, the dismutation between triosephosphate and pyruvic acid could still occur, and synthesis