Phenylalanine degradation (WP573)

Saccharomyces cerevisiae

While Saccharomyces cerevisiae can use most amino acids as their sole nitrogen source, they can only use a few amino acids as a carbon source to support growth (CITS:[Large86][Cooper82]). This is in contrast to most eukaryotes and some fungi, which can metabolize amino acids completely, utilizing them as sole sources of carbon and nitrogen (CITS:[Stryer88][Large 86]). S. cerevisiae degrade the aromatic amino acids (phenylalanine, tyrosine, and tryptophan) and the branched-chain amino acids (valine, leucine, and iso-leucine) via the Ehrlich pathway (CITS:[Sentheshanmuganathan60][10989420]). This pathway is comprised of the following steps: 1) deamination of the amino acid to the corresponding alpha-keto acid; 2) decarboxylation of the resulting alpha-keto acid to the respective aldehyde; and, 3) reduction of the aldehyde to form the corresponding long chain or complex alcohol, known as a fusel alcohol or fusel oil (CITS:[10989420][Large 86]). Fusel alcohols are important flavor and aroma compounds in yeast-fermented food products and beverages (as reported in (CITS:[9546164]). Aro10p appears to be the primary decarboxylase catalyzing the second step in phenylalanine degradation (CITS:[12902239][15933030]). Although Vulrahan et. al. (2003) (CITS:[12902239]) found that THI3 does not encode an active phenylpyruvate decarboxylase, they found Thi3p was required in conjunction with one of the pyruvate decarboxylases Pdc1p, Pdc5p or Pdc6p for the ARO10-independent decarboxylase activity. The main uptake systems for utilizing aromatic amino acids appear to be Gap1p, a general amino acid permease, and Wap1p, an inducible amino acid permease with wide substrate specificity (CITS:[10207060]) SOURCE: SGD pathways,


Meredith Braymer , Daniela Digles , Egon Willighagen , and Eric Weitz


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Saccharomyces cerevisiae



Pathway Ontology

phenylalanine degradation pathway


Label Type Compact URI Comment
L-glutamate Metabolite cas:56-86-0
L-phenylalanine Metabolite cas:63-91-2
phenylacetaldehyde Metabolite cas:122-78-1
phenylpyruvate Metabolite chemspider:3784710
H2O Metabolite chemspider:937
2-oxoglutarate Metabolite chemspider:144236
phenylethanol Metabolite chemspider:5830
PDC1 GeneProduct sgd:S000004034
PDC5 GeneProduct sgd:S000004124
ARO10 GeneProduct sgd:S000002788
PDC6 GeneProduct sgd:S000003319
SFA1 GeneProduct sgd:S000002327
ADH1 GeneProduct sgd:S000005446
ADH2 GeneProduct sgd:S000004918
ADH3 GeneProduct sgd:S000004688
ADH5 GeneProduct sgd:S000000349
ADH4 GeneProduct sgd:S000003225
ARO9 GeneProduct sgd:S000001179


  1. Phenylalanine- and tyrosine-auxotrophic mutants of Saccharomyces cerevisiae impaired in transamination. Urrestarazu A, Vissers S, Iraqui I, Grenson M. Mol Gen Genet. 1998 Jan;257(2):230–7. PubMed Europe PMC Scholia
  2. Characterisation of Saccharomyces cerevisiae ARO8 and ARO9 genes encoding aromatic aminotransferases I and II reveals a new aminotransferase subfamily. Iraqui I, Vissers S, Cartiaux M, Urrestarazu A. Mol Gen Genet. 1998 Jan;257(2):238–48. PubMed Europe PMC Scholia
  3. The catabolism of amino acids to long chain and complex alcohols in Saccharomyces cerevisiae. Dickinson JR, Salgado LEJ, Hewlins MJE. J Biol Chem. 2003 Mar 7;278(10):8028–34. PubMed Europe PMC Scholia
  4. Identification and characterization of phenylpyruvate decarboxylase genes in Saccharomyces cerevisiae. Vuralhan Z, Morais MA, Tai SL, Piper MDW, Pronk JT. Appl Environ Microbiol. 2003 Aug;69(8):4534–41. PubMed Europe PMC Scholia
  5. Physiological characterization of the ARO10-dependent, broad-substrate-specificity 2-oxo acid decarboxylase activity of Saccharomyces cerevisiae. Vuralhan Z, Luttik MAH, Tai SL, Boer VM, Morais MA, Schipper D, et al. Appl Environ Microbiol. 2005 Jun;71(6):3276–84. PubMed Europe PMC Scholia