Isoleucine degradation (WP178)

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. 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. S. cerevisiae degrade the branched-chain amino acids (iso-leucine, leucine, and valine) and the aromatic amino acids (tryptophan, phenylalanine, and tyrosine) via the Ehrlich pathway. 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. Fusel alcohols are important flavor and aroma compounds in yeast-fermented food products and beverages 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. The initial transamination step in iso-leucine degradation can be catalyzed by either of the branched-chain amino acid transaminases BAT1 (mitochondrial) or BAT2 (cytosolic). The subsequent decarboxylation step can be catalyzed by any one of the five decarboxylases (Pdc1p, Pdc5p, Pdc6p, Thi3p, and Aro10p) and the final step can be catalyzed by any one of six alcohol dehydrogenases (Adh1p, Adh2p, Adh3p, Adh4p, Adh5p, and Sfa1p). SOURCE: SGD pathways, http://pathway.yeastgenome.org/server.html

Authors

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

Activity

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Organisms

Saccharomyces cerevisiae

Communities

Annotations

Pathway Ontology

classic metabolic pathway isoleucine degradation pathway

Participants

Label Type Compact URI Comment
L-isoleucine Metabolite chebi:58045
2-methylbutanal Metabolite chebi:16182
NAD+ Metabolite chebi:57540
NADH Metabolite chebi:57945
L-glutamate Metabolite cas:56-86-0
H+ Metabolite chebi:15378
2-oxoglutarate Metabolite chebi:16810
2-methylbutanol Metabolite chebi:48945
CO2 Metabolite chebi:16526
(S)-3-methyl-2-oxopentanoate Metabolite chebi:35146
BAT2 GeneProduct sgd:S000003909
BAT1 GeneProduct sgd:S000001251
PDC1 GeneProduct sgd:S000004034
THI3 GeneProduct sgd:S000002238
ARO10 GeneProduct sgd:S000002788
PDC6 GeneProduct sgd:S000003319
PDC5 GeneProduct sgd:S000004124
SFA1 GeneProduct ensembl:YDL168W
ADH5 GeneProduct ensembl:YBR145W
ADH4 GeneProduct ensembl:YGL256W

References

  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. An investigation of the metabolism of isoleucine to active Amyl alcohol in Saccharomyces cerevisiae. Dickinson JR, Harrison SJ, Dickinson JA, Hewlins MJ. J Biol Chem. 2000 Apr 14;275(15):10937–42. PubMed Europe PMC Scholia
  4. Branched-chain-amino-acid transaminases of yeast Saccharomyces cerevisiae. Prohl C, Kispal G, Lill R. Methods Enzymol. 2000;324:365–75. PubMed Europe PMC Scholia
  5. URL: https://pathway.yeastgenome.org/YEAST/NEW-IMAGE?type=PATHWAY&object=PWY3O-4109