Malonate oxidation by dry cells and cell-free extracts of Pseudomonas fluorescens.

It was previously shown that oxygen uptake per mole of substrate, using resting cell suspensions of a strain of Pseudomonas fluorescens, was significantly higher on malonate than on acetate (Wolfe and Rittenberg, 1953). If malonate is anaerobically decarboxylated to carbon dioxide and acetate, one would expect comparable oxygen consumption on the two substrates. The observed difference in uptake, as well as other data, suggested that acetate was not a direct intermediate in malonate degradation. Recently evidence has been presented that established AcCoA3 as a product of malonate decarboxylation and the participation of a coupled CoA transferase system in the decarboxylase reaction (Wolfe and Rittenberg, 1954; Wolfe et al., 1954b; Hayaishi, 1954). These findings and other data (Wolfe et al., 1954a; Hayaishi, 1953) make it apparent that the mechanism of malonate decarboxylation in P. fluorescens is more complex than that reported by Gray (1952) for P. aeruginosa. The establishment of AcCoA as a direct intermediate in malonate metabolism initially seemed to offer an explanation for the oxygen consumption data mentioned above. However, further oxidative studies with dry cells and cell-free extracts, presented in this paper, demonstrate that some compound in addition to AcCoA is formed and oxidized in the malonate decarboxylase reaction.