The Dissimilation of Higher Dicarboxylic Acids by Pseudomonas fluorescens

This work provides presumptive evidnce that Pseudomonas fluorescens metabolizes the higher homologs (C 6 to C 10 ) of the saturated dicarboxylic acid series by β‐oxidation, mediated by a specific series of inducible enzymes. The initial step in the metabolism of four of these acids (pimelic, suberic, azelaic and sebacic acids) is the formation of the corresponding CoA‐ester. This step is mediated by a single, inducible thiokinase. A thiokinaseless mutant can utilize none of these four dicarboxylic acids. Although adipic acid can also apparently be activated to a slight extent by the thiokinase, the unimpaired ability of the thiokinaseless mutant to grow with adipate shows that there is a second mechanism for the activation of this member of the series. Adipic acid is also activated by an inducible adipate: succinyl‐CoA transferase, which cannot use the higher homologs of the dicarboxylic acid series as CoA acceptors (with the exception of pimelic acid, which is weakly activated). This transferase is probably responsible for adipic acid activation in vivo . Inducible dehydrogenases which can oxidise acyl‐CoA and β‐hydroxyacyl‐CoA derivatives of the higher dicarboxylic acids were also demonstrated, but their substrate specificities were not determined. The former enzyme can dehydrogenate both adipyl‐CoA and azelayl‐CoA; and the latter, β‐hydroxyadipyl‐CoA. A mutant unable to form the enzyme with β‐hydroxy‐adipyl‐CoA dehydrogenase activity cannot grow with any dicarboxylic acid of the C 6 to C 10 series.