Molecular characterization of the phenolic acid metabolism in the lactic acid bacteria Lactobacillus plantarum

The lactic acid bacteria Lactobacillus plantarum displays substrate-inducible decarboxylase activities on p-coumaric, caffeic and ferulic acids. Purification of the p-coumaric acid decarboxylase (PDC) was performed. Sequence of the N-terminal part of the PDC led to the cloning of the corresponding pdc gene. Expression of this gene in Escherichia coli revealed that PDC displayed a weak activity on ferulic acid, detectable in vitro in the presence of ammonium sulfate. Transcriptional studies of this gene in L. plantarum demonstrated that the pdc transcription is phenolic aciddependent. A mutant deficient in the PDC activity, designated LPD1, was constructed to study phenolic acid alternate pathways in L. plantarum. LPD1 mutant strain remained able to metabolize weakly p-coumaric and ferulic acids into vinyl derivatives or into substituted phenyl propionic acids. These results indicate that L. plantarum has a second acid phenol decarboxylase enzyme and also displays inducible acid phenol reductase activity. Finally, PDC activity was shown to confer a selective advantage for LPNC8 grown in acidic media supplemented with p-coumaric acid, compared to the LPD1 mutant devoid of PDC activity. phenolic acid / phenolic acid decarboxylase / phenolic acid reductase / Lactobacillus plantarum Rsum -Caractrisation molculaire du mtabolisme des acides phnol chez Lactobacillus plantarum. La bactrie lactique Lactobacillus plantarum est capable de dcarboxyler les acides p-coumarique, frulique et cafique. La purification de l'acide p-coumarique dcarboxylase (PDC) a t ralise. La dtermination de la squence N-terminale de cette enzyme a permis de cloner le gne pdc correspondant. L'expression de ce gne chez Escherichia coli rvle que la PDC possde une faible activit sur l'acide frulique, dtectable in vitro uniquement en prsence de sulfate d'ammonium. L'tude des ARN messagers du gne pdc chez L. plantarum montre que la transcription de ce gne dpend des acides phnols. La construction d'un mutant dficient pour l'activit PDC, nomm LPD1 a t ralise afin d'tudier les mtabolismes secondaires des acides phnols chez L. plantarum. Ce mutant LPD1 reste capable de dgrader les acides phnols en drivs de type vinyl phnol ou en acides phnyl propioniques. Ces rsultats indiquent que L. plantarum possde une seconde acide