This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: Ehrlich pathway
|Superclasses:||Degradation/Utilization/Assimilation → Amino Acids Degradation → Phenylalanine Degradation|
Some taxa known to possess this pathway include : Saccharomyces cerevisiae
Expected Taxonomic Range: Fungi
While Saccharomyces cerevisiae can utilize only a limited range of carbon sources [Barnett92] it can obtain its nitrogen from many different sources, including most amino acids [Large68]. The most common mechanism for retrieving the nitrogen from amino acids is transamination, using 2-oxoglutarate or other 2-oxo acids as amino acceptors. This process leaves the carbon skeleton of the amino acid intact, in the form of a 2-oxo acid. In a few cases the resulting 2-oxo acid can be directly fed into central metabolism (such as the case of L-alanine and its derived 2-keto acid, pyruvate). In most cases, though, the 2-oxo acids resulting from transamination are not intermediates of central metabolism, and are excreted from the cells after some transformation.
An important and common pathway for catabolism of amino acids by yeast is the Ehrlich pathway [Ehrlich07]. In this pathway, following transamination of an amino acid into the corresponding 2-oxo acid, the 2-oxo acid is decarboxylated to an aldehyde. Depending on the redox status of the cells [Vuralhan03], the aldehydes can then be either reduced (by alcohol dehydrogenases) to alcohols, which are called collectively "fusel alcohols", or oxidized by aldehyde dehydrogenases to organic acids ("fusel acids") [Vuralhan05].
Aromatic amino acids, such as L-phenylalanine, can be used as a nitrogen source, but not as a carbon source. Following the transamination of L-phenylalanine to 2-oxo-3-phenylpropanoate, the 2-oxo acid is converted to phenylacetaldehyde and eventually 2-phenylethanol, which is excreted from the cell [Vuralhan03]. The first step is performed by either of two aromatic amino acid transaminases. aromatic amino acid aminotransferase II is the main catabolic enzyme, and accepts 2-oxo-3-phenylpropanoate, pyruvate or 4-hydroxyphenylpyruvate, but not 2-oxoglutarate, as the amino acceptor [Kradolfer82, Urrestarazu98]. However, a reaction utilizing 2-oxoglutarate as the amino acceptor has also been demonstrated, and is likely catalyzed by aromatic amino acid aminotransferase I [Kradolfer82, Urrestarazu98, Iraqui98].
Once transaminated, the 2-oxo acid is decarboxylated by either of four decarboxylases, although recent results suggest that the main decarboxylase performing this reaction in vivo is the 2-oxo acid decarboxylase encoded by the gene ARO10, whose expression increased 30-fold when L-phenylalanine replaced ammonia as the culture's nitrogen source [Vuralhan05].
The last step of this pathway can be performed by any of the yeast alcohol dehydrogenases [Dickinson03].
Iraqui98: Iraqui I, Vissers S, Cartiaux M, Urrestarazu A (1998). "Characterisation of Saccharomyces cerevisiae ARO8 and ARO9 genes encoding aromatic aminotransferases I and II reveals a new aminotransferase subfamily." Mol Gen Genet 257(2);238-48. PMID: 9491083
Kradolfer82: Kradolfer P, Niederberger P, Hutter R (1982). "Tryptophan degradation in Saccharomyces cerevisiae: characterization of two aromatic aminotransferases." Arch Microbiol 133(3);242-8. PMID: 6763508
Urrestarazu98: Urrestarazu A, Vissers S, Iraqui I, Grenson M (1998). "Phenylalanine- and tyrosine-auxotrophic mutants of Saccharomyces cerevisiae impaired in transamination." Mol Gen Genet 257(2);230-7. PMID: 9491082
Vuralhan03: Vuralhan Z, Morais MA, Tai SL, Piper MD, Pronk JT (2003). "Identification and characterization of phenylpyruvate decarboxylase genes in Saccharomyces cerevisiae." Appl Environ Microbiol 69(8);4534-41. PMID: 12902239
Vuralhan05: Vuralhan Z, Luttik MA, Tai SL, Boer VM, Morais MA, Schipper D, Almering MJ, Kotter P, Dickinson JR, Daran JM, Pronk JT (2005). "Physiological characterization of the ARO10-dependent, broad-substrate-specificity 2-oxo acid decarboxylase activity of Saccharomyces cerevisiae." Appl Environ Microbiol 71(6);3276-84. PMID: 15933030
Boer03: Boer VM, de Winde JH, Pronk JT, Piper MD (2003). "The genome-wide transcriptional responses of Saccharomyces cerevisiae grown on glucose in aerobic chemostat cultures limited for carbon, nitrogen, phosphorus, or sulfur." J Biol Chem 278(5);3265-74. PMID: 12414795
Cheraiti08: Cheraiti N, Sauvage FX, Salmon JM (2008). "Acetaldehyde addition throughout the growth phase alleviates the phenotypic effect of zinc deficiency in Saccharomyces cerevisiae." Appl Microbiol Biotechnol 77(5);1093-109. PMID: 17938904
Collier72: Collier RH, Kohlhaw G (1972). "Nonidentity of the aspartate and the aromatic aminotransferase components of transaminase A in Escherichia coli." J Bacteriol 1972;112(1);365-71. PMID: 4404056
Dickinson00: Dickinson JR, Harrison SJ, Dickinson JA, Hewlins MJ (2000). "An investigation of the metabolism of isoleucine to active Amyl alcohol in Saccharomyces cerevisiae." J Biol Chem 275(15);10937-42. PMID: 10753893
Dickinson97: Dickinson JR, Lanterman MM, Danner DJ, Pearson BM, Sanz P, Harrison SJ, Hewlins MJ (1997). "A 13C nuclear magnetic resonance investigation of the metabolism of leucine to isoamyl alcohol in Saccharomyces cerevisiae." J Biol Chem 272(43);26871-8. PMID: 9341119
Emes73: Emes AV, Hassall H (1973). "The degradation of L-histidine in the rat. The formation of imidazolylpyruvate, imidazolyl-lactate and imidazolylpropionate." Biochem J 136(3);649-58. PMID: 4360716
Fauchon02: Fauchon M, Lagniel G, Aude JC, Lombardia L, Soularue P, Petat C, Marguerie G, Sentenac A, Werner M, Labarre J (2002). "Sulfur sparing in the yeast proteome in response to sulfur demand." Mol Cell 9(4);713-23. PMID: 11983164
Feldmann94: Feldmann H, Aigle M, Aljinovic G, Andre B, Baclet MC, Barthe C, Baur A, Becam AM, Biteau N, Boles E (1994). "Complete DNA sequence of yeast chromosome II." EMBO J 13(24);5795-809. PMID: 7813418
Flikweert96: Flikweert MT, Van Der Zanden L, Janssen WM, Steensma HY, Van Dijken JP, Pronk JT (1996). "Pyruvate decarboxylase: an indispensable enzyme for growth of Saccharomyces cerevisiae on glucose." Yeast 12(3);247-57. PMID: 8904337
Ganzhorn87: Ganzhorn AJ, Green DW, Hershey AD, Gould RM, Plapp BV (1987). "Kinetic characterization of yeast alcohol dehydrogenases. Amino acid residue 294 and substrate specificity." J Biol Chem 262(8);3754-61. PMID: 3546317
Gonda10: Gonda I, Bar E, Portnoy V, Lev S, Burger J, Schaffer AA, Tadmor Y, Gepstein S, Giovannoni JJ, Katzir N, Lewinsohn E (2010). "Branched-chain and aromatic amino acid catabolism into aroma volatiles in Cucumis melo L. fruit." J Exp Bot 61(4);1111-23. PMID: 20065117
Kellermann86: Kellermann E, Seeboth PG, Hollenberg CP (1986). "Analysis of the primary structure and promoter function of a pyruvate decarboxylase gene (PDC1) from Saccharomyces cerevisiae." Nucleic Acids Res 14(22);8963-77. PMID: 3537965
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