Leucine degradation (WP354)

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 branched-chain amino acids (leucine, iso-leucine, and valine) and the aromatic amino acids (tryptophan, phenylalanine, and tyrosine) 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]). Each of the three steps in branched-chain amino acid degradation can be catalyzed by more than one isozyme; which enzyme is used appears to depend on the amino acid, the carbon source and the stage of growth of the culture (CITS:[12499363]). In leucine degradation, Thi3p is believed to be the major decarboxylase (CITS: [12499363]). SOURCE: SGD pathways, http://pathway.yeastgenome.org/server.html


Jessica Heckman , Daniela Digles , Egon Willighagen , and Eric Weitz


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Saccharomyces cerevisiae



Pathway Ontology

leucine degradation pathway


Label Type Compact URI Comment
L-leucine Metabolite cas:61-90-5
L-glutamate Metabolite cas:56-86-0
BAT1 GeneProduct sgd:S000001251
BAT2 GeneProduct sgd:S000003909
ARO10 GeneProduct sgd:S000002788
THI3 GeneProduct sgd:S000002238


  1. Two yeast homologs of ECA39, a target for c-Myc regulation, code for cytosolic and mitochondrial branched-chain amino acid aminotransferases. Eden A, Simchen G, Benvenisty N. J Biol Chem. 1996 Aug 23;271(34):20242–5. PubMed Europe PMC Scholia
  2. Mitochondrial and cytosolic branched-chain amino acid transaminases from yeast, homologs of the myc oncogene-regulated Eca39 protein. Kispal G, Steiner H, Court DA, Rolinski B, Lill R. J Biol Chem. 1996 Oct 4;271(40):24458–64. PubMed Europe PMC Scholia
  3. A 13C nuclear magnetic resonance investigation of the metabolism of leucine to isoamyl alcohol in Saccharomyces cerevisiae. Dickinson JR, Lanterman MM, Danner DJ, Pearson BM, Sanz P, Harrison SJ, et al. J Biol Chem. 1997 Oct 24;272(43):26871–8. PubMed Europe PMC Scholia
  4. Pyruvate decarboxylase catalyzes decarboxylation of branched-chain 2-oxo acids but is not essential for fusel alcohol production by Saccharomyces cerevisiae. ter Schure EG, Flikweert MT, van Dijken JP, Pronk JT, Verrips CT. Appl Environ Microbiol. 1998 Apr;64(4):1303–7. PubMed Europe PMC Scholia
  5. An investigation of the metabolism of valine to isobutyl alcohol in Saccharomyces cerevisiae. Dickinson JR, Harrison SJ, Hewlins MJ. J Biol Chem. 1998 Oct 2;273(40):25751–6. PubMed Europe PMC Scholia
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  9. 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