Novel scheme for biosynthesis of aryl metabolites from L-phenylalanine in the fungus Bjerkandera adusta

Appl Environ Microbiol. 2000 Apr;66(4):1517-22. doi: 10.1128/AEM.66.4.1517-1522.2000.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Basidiomycota / growth & development
  • Basidiomycota / metabolism*
  • Benzaldehydes / metabolism
  • Benzoic Acid / metabolism
  • Benzyl Alcohols / metabolism
  • Carbon Radioisotopes / metabolism
  • Culture Media
  • Hydrocarbons, Aromatic / metabolism*
  • Phenylalanine / metabolism*

Substances

  • Benzaldehydes
  • Benzyl Alcohols
  • Carbon Radioisotopes
  • Culture Media
  • Hydrocarbons, Aromatic
  • Phenylalanine
  • Benzoic Acid
  • benzaldehyde