Novel scheme for biosynthesis of aryl metabolites from L-phenylalanine in the fungus Bjerkandera adusta.
Aryl metabolite biosynthesis was studied in the white rot fungus Bjerkandera adusta cultivated in a liquid medium supplemented with L-phenylalanine. Aromatic compounds were analyzed by gas chromatography-mass spectrometry following addition of labelled precursors ((14)C- and (13)C-labelled L-phenylalanine), which did not interfere with fungal metabolism. The major aromatic compounds identified were benzyl alcohol, benzaldehyde (bitter almond aroma), and benzoic acid. Hydroxy- and methoxybenzylic compounds (alcohols, aldehydes, and acids) were also found in fungal cultures. Intracellular enzymatic activities (phenylalanine ammonia lyase, aryl-alcohol oxidase, aryl-alcohol dehydrogenase, aryl-aldehyde dehydrogenase, lignin peroxidase) and extracellular enzymatic activities (aryl-alcohol oxidase, lignin peroxidase), as well as aromatic compounds, were detected in B. adusta cultures. Metabolite formation required de novo protein biosynthesis. Our results show that L-phenylalanine was deaminated to trans-cinnamic acid by a phenylalanine ammonia lyase and trans-cinnamic acid was in turn converted to aromatic acids (phenylpyruvic, phenylacetic, mandelic, and benzoylformic acids); benzaldehyde was a metabolic intermediate. These acids were transformed into benzaldehyde, benzyl alcohol, and benzoic acid. Our findings support the hypothesis that all of these compounds are intermediates in the biosynthetic pathway from L-phenylalanine to aryl metabolites. Additionally, trans-cinnamic acid can also be transformed via beta-oxidation to benzoic acid. This was confirmed by the presence of acetophenone as a beta-oxidation degradation intermediate. To our knowledge, this is the first time that a beta-oxidation sequence leading to benzoic acid synthesis has been found in a white rot fungus. A novel metabolic scheme for biosynthesis of aryl metabolites from L-phenylalanine is proposed.
Lapadatescu
C
C
Laboratoire de Recherches Sur les Arômes (LRSA), Institut National de la Recherche Agronomique, 21034 Dijon cedex, France.
Giniès
C
C
Le Quéré
J L
JL
Bonnarme
P
P
D001487:Basidiomycota / Q000254:growth & development / Q000378:metabolism*; D001547:Benzaldehydes / Q000378:metabolism; D019817:Benzoic Acid / Q000378:metabolism; D001592:Benzyl Alcohols / Q000378:metabolism; D002250:Carbon Radioisotopes / Q000378:metabolism; D003470:Culture Media; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism*
D001547:Benzaldehydes; D001592:Benzyl Alcohols; D002250:Carbon Radioisotopes; D003470:Culture Media; D006841:Hydrocarbons, Aromatic; D010649:Phenylalanine; D019817:Benzoic Acid; C032175:benzaldehyde