Date of this Version
Published in Transactions of the Nebraska Academy of Sciences, Volume 1 (1972).
A strain of Pseudomonas non-fluorescens has shown to metabolize certain phenolic compounds through a pathway containing D-malic acid. This same bacterium is able to oxidize D-malate slowly when it is used as the sole carbon source, but is unable to grow on it. Possible pathways and explanations of this phenomena are postulated.
In recent years the metabolism of malate enantiomers in various species of Pseudomonas has been the subject of considerable investigation. This results from the fact that the microbial metabolism of the dihydroxphenol, gentisic acid, has been shown to include D-malate in the metabolic chain (Hopper, Chapman, and Dagley, 1968, p. 65). This compound is not the naturally occurring form of malate found in the tricarboxylic acid cycle, but its enantiomer.
In general, the process of splitting the stable benzene ring is initiated by the addition of first one, then two hydroxy-groups to the benzene ring by a series of enzymes known as "monooxygenases." A second series of enzymes known as "dioxygenases" are responsible for the fission of the benzene nucleus, and in the particular case of gentisic acid, the a-keto dicarboxylic acid, maleylpyruvate, is formed (Figure 1) (Dagley, 1967, pp. 287-288).