Abstract
Slade et al. 1 have shown the fixation of C12O2 in the carboxyl group of acetic acid by Aerobacter indolegenes and Clostridium welchii. The present report provides evidence for the occurrence of the reaction by a cleavage of a C4-dicarboxylic acid. Participation of C2-compounds in the synthesis of 2, 3-butylene glycol by Aerobacter indologenes is also shown to occur.
Two types of acetic acid were synthesized, (1) CH3 C13OOH and (2) C13H3 C13OOH2. Succinic acid (C13OOH · CH2 · CH2 · COOH) was recovered from various bacterial fermentation. Salts of the acids were added to cell suspensions of A. indologenes in the presence of glucose under an atmosphere of nitrogen. The concentration of C13 was determined by mass spectrometer analysis. The normal complement of C13 is 1.09%.
The distribution of C13 on the addition of the acids is shown in Table I. Succinic acid formed in the presence of CH3 · C13OOH contains C13 exclusively in the carboxyl carbons (Table II). Succinate was not formed by a synthesis of pyruvate by C1 and C2 addition, followed by C3 and C1 addition to oxalacetate, for the succinate formed would have contained C13 in the methylene carbons. Thus, succinic acid is formed by means of a carbon to carbon linkage involving the carbon† atom originally present in the methyl group of acetic acid. The general reaction is:
Equation
The reaction is presented with the reservation that acetic acid may or may not be the actual C2 compound involved in the condensation reaction.
Succinate formed in the presence of C3 · C1313H3 · C13OOH contains C13 eqully distributed between the methyl and carboxyl carbons (Table II). This is in agreement with the above reaction and proves that the acetate was not oxidized to C13O2 and the succinate formed by the Wood and Werkman reaction; otherwise the C13 would have been found exclusively in the carboxyl carbons.
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