The Catabolism of Amino Acids to Long Chain and Complex Alcohols in Saccharomyces cerevisiae

Abstract

The catabolism of phenylalanine to 2-phenylethanol and of tryptophan to tryptophol were studied by13C NMR spectroscopy and gas chromatography-mass spectrometry. Phenylalanine and tryptophan are first deaminated (to 3-phenylpyruvate and 3-indolepyruvate, respectively) and then decarboxylated. This decarboxylation can be effected by any of Pdc1p, Pdc5p, Pdc6p, or Ydr380wp; Ydl080cp has no role in the catabolism of either amino acid. We also report that in leucine catabolism Ydr380wp is the minor decarboxylase. Hence, all amino acid catabolic pathways studied to date use a subtly different spectrum of decarboxylases from the five-membered family that comprises Pdc1p, Pdc5p, Pdc6p, Ydl080cp, and Ydr380wp. Using strains containing all possible combinations of mutations affecting the seven AAD genes (putativearyl alcohol dehydrogenases), fiveADH genes, and SFA1, showed that the final step of amino acid catabolism (conversion of an aldehyde to a long chain or complex alcohol) can be accomplished by any one of the ethanol dehydrogenases (Adh1p, Adh2p, Adh3p, Adh4p, Adh5p) or by Sfa1p (formaldehyde dehydrogenase.) The catabolism of phenylalanine to 2-phenylethanol and of tryptophan to tryptophol were studied by13C NMR spectroscopy and gas chromatography-mass spectrometry. Phenylalanine and tryptophan are first deaminated (to 3-phenylpyruvate and 3-indolepyruvate, respectively) and then decarboxylated. This decarboxylation can be effected by any of Pdc1p, Pdc5p, Pdc6p, or Ydr380wp; Ydl080cp has no role in the catabolism of either amino acid. We also report that in leucine catabolism Ydr380wp is the minor decarboxylase. Hence, all amino acid catabolic pathways studied to date use a subtly different spectrum of decarboxylases from the five-membered family that comprises Pdc1p, Pdc5p, Pdc6p, Ydl080cp, and Ydr380wp. Using strains containing all possible combinations of mutations affecting the seven AAD genes (putativearyl alcohol dehydrogenases), fiveADH genes, and SFA1, showed that the final step of amino acid catabolism (conversion of an aldehyde to a long chain or complex alcohol) can be accomplished by any one of the ethanol dehydrogenases (Adh1p, Adh2p, Adh3p, Adh4p, Adh5p) or by Sfa1p (formaldehyde dehydrogenase.) gas chromatography-mass spectrometry It is well known that Saccharomyces cerevisiae converts sugars to ethanol using the glycolytic pathway. In addition, it also produces a number of long chain and complex alcohols including isoamyl alcohol, isobutanol, active amyl alcohol, 2-phenylethanol, and tryptophol (1Webb A.D. Ingraham J.L. Adv. Appl. Microbiol. 1963; 5: 317-353Google Scholar). These are all important flavor and aroma compounds in yeast-fermented products and have interesting organoleptic properties in their own right, many of which are both concentration- and context-dependent. These long chain and complex alcohols are the end products of amino acid catabolism. In this respect the pathways used by S. cerevisiae are very different from those in other eukaryotes that have been well understood for many years (2Bender D.A. Amino Acid Metabolism. John Wiley & Sons, Inc., New York1975Google Scholar). We have sought to discover the genes and enzymes used by S. cerevisiae in the catabolism of leucine to isoamyl alcohol (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar), valine to isobutanol (4Dickinson J.R. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1998; 273: 25751-25756Google Scholar), and isoleucine to active amyl alcohol (5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar). In all cases, the general sequence of biochemical reactions is similar, but the details for the formation of the individual alcohols are surprisingly different. The branched-chain amino acids are first deaminated to the corresponding α-ketoacids (α-ketoisocaproic acid from leucine, α-ketoisovaleric acid from valine, and α-keto-β-methylvaleric acid from isoleucine). There are significant differences in the way each α-ketoacid is subsequently decarboxylated. In the leucine degradation pathway the major decarboxylase is encoded by YDL080c. Consequently, we refer to this open reading frame as KID1 for ketoisocaproate decarboxylase 1 (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar). In valine degradation any one of the three isozymes of pyruvate decarboxylase encoded by PDC1, PDC5, andPDC6 will decarboxylate α-ketoisovalerate (4Dickinson J.R. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1998; 273: 25751-25756Google Scholar), and in isoleucine catabolism any one of the family of decarboxylases encoded by PDC1, PDC5, PDC6, YDL080c, or YDR380w is sufficient for the conversion of isoleucine to active amyl alcohol (5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar). There are three important questions that remain unanswered. First, our earlier work had shown that the YDL080c-encoded decarboxylase was the major route of decarboxylation of α-ketoisocaproate but that there was at least one other unidentified decarboxylase involved in leucine catabolism. This enzyme should be identified, and its metabolic contribution should be quantified. Second, other than the fact that tryptophan is the precursor of tryptophol, and phenylalanine is the precursor of 2-phenylethanol (1Webb A.D. Ingraham J.L. Adv. Appl. Microbiol. 1963; 5: 317-353Google Scholar), little else is known about the genes and enzyme-catalyzed steps involved in the catabolism of these two aromatic amino acids in S. cerevisiae except that Ydr380wp has been suggested as a potential indolepyruvate decarboxylase (the enzyme that would be required for the conversion of indolepyruvate to indole acetaldehyde if tryptophan is catabolized in an analogous way to the branched-chain amino acids) (6Iraqui I. Vissers S. Andre B. Urrestarazu A. Mol. Cell. Biol. 1999; 19: 3360-3371Google Scholar). Third, the final stage of long chain and complex alcohol formation has always been assumed to be an alcohol dehydrogenase-catalyzed step (1Webb A.D. Ingraham J.L. Adv. Appl. Microbiol. 1963; 5: 317-353Google Scholar), but this has never been rigorously examined. Because yeast has 20 genes that could potentially encode this activity, seven putative aryl alcohol dehydrogenase genes (7Delneri D. Gardner D.C.J. Oliver S.G. Genetics. 1999; 153: 1591-1600Google Scholar, 8Delneri D. Gardner D.C.J. Bruschi C.V. Oliver S.G. Yeast. 1999; 15: 1681-1689Google Scholar) and 13 other alcohol dehydrogenase genes, ADH1,ADH2, ADH3, ADH4, ADH5,SFA1, BDH1, putative BDH2 (YAL061w),SOR1, putative SOR2 (YDL246c), XDH1, the cinnamyl alcohol dehydrogenase CDH1 (YCR105w), and the recently proposed ADH6 (YMR318c) (9Larroy C. Fernández M.R. González E. Parés X. Biosca J.A. Biochem. J. 2000; 361: 163-172Google Scholar), it is also necessary to discover which of these gene products are required for long chain and complex alcohol formation. This paper addresses all three questions. The strains used are shown in Table I. IWD72 is the wild-type strain that we have used for all studies of amino acid catabolism. Strain YPH499 is the wild-type parent of strain AAD7x. Standard genetic techniques were used in all cases (11Sherman F. Methods Cell Biol. 1975; 11: 189-199Google Scholar, 12Mortimer R.K. Hawthorn D.C. Methods Cell Biol. 1975; 11: 221-233Google Scholar). Strain 59.2.1 was produced by crossing strain Y04623 (MAT a his3Δ1 leu2Δ0 met15Δ0 ura3Δ0 adh4::kanMX4 from EUROSCARF) with strain 58.3.4 (MATα ura3–52 lys2–801 ade2–101 trp1Δ63 his3Δ200 leu2Δ1). Strain 58.3.4 had been produced in an earlier cross between IWD72 and YPH499. Strain 60.3.3 was produced by mating strain 900–17-101a to strain 59.2.1 and sporulation of the resultant diploid. Strain 61.1.1 was produced by sporulating strain Y26236 (MATa/MATα his3Δ1/his3Δ1 leu2Δ0/leu2Δ0 lys2Δ0/LYS2 MET15/met15Δ0 ura3Δ0/ura3Δ0 adh1::kanMX4/ADH1 from EUROSCARF) and then dissection of the ascospores. Strain ESH380w was produced by a cross between strain Y14216 (MATα his3Δ1 leu2Δ0 lys2Δ0 ura3Δ0 ydr380w::kanMX4 from EUROSCARF) and YSH5.127.17C. In all cases haploid progeny carrying a single gene disrupted with the kanMX4 cassette were identified by their ability to grow in the presence of G418 (Geneticin) at 200 μg/ml. Strain 62.3.17 was produced by crossing strain 60.3.3 and strain Y13284(MATα his3Δ1 leu2Δ0 lys2Δ0 ura3Δ0 adh5::kanMX4 from EUROSCARF). Strain 66.1.3 was produced by crossing strain 60.3.3 and strain 63.2.1 (MATα his3Δ1 sfa1::kanMX4), the latter having been produced earlier by crossing IWD72 and Y03866. In progeny containing two alleles that were both disrupted with kanMX4, the presence of the adh4::kanMX4 andadh5::kanMX4 alleles or theadh4::kanMX4 andsfa1::kanMX4 alleles were confirmed by diagnostic polymerase chain reactions using specific primers that yielded products that were unique to each disruption allele.Table IYeast strains usedStrainGenotypeSource or reference51.1.3MATα ura3 ydl080c∷kanMX4(5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar)55.2.1MAT a ade8 leu2Δ0 ydr380w∷kanMX4(5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar)57.2.13MATα ade8 leu2 ura3 ydl080c∷kanMX4 ydr380w∷kanMX4(5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar)YSH5.127.17CMAT a leu2–3,112 ura3–52, trp1–92 pdc1Δ∷LEU2 pdc5∷URA3 pdc6∷TRP1 GALS. HohmannaDepartment of Cell and Molecular Biology/Microbiology, Göteborg University, Box 462, S-405 30 Göteborg, Sweden.JRD815–1.2MAT a pdc1Δ∷LEU2 pdc5∷URA3 pdc6∷TRP1 ydl080c∷kanMX4(3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar)ESH380wMATα his3Δ1 pdc1Δ∷LEU2 pdc5∷URA3 pdc6∷TRP1 ydr380w∷kanMX4This study56.9.2MAT a pdc1Δ∷LEU2 pdc5∷URA3 pdc6∷TRP1 ydl080c∷kanMX4 ydr380w∷kanMX4(5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar)53.1.4MATα lys2∷hisG met8 ura3 lpd∷URA3(5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar)IWD72MATα(10Dickinson J.R. Dawes I.W. J. Gen. Microbiol. 1992; 138: 2029-2033Google Scholar)61.1.1MAT a his3Δ1 leu2Δ0 lys2Δ0 met15Δ0 ura3Δ0 adh1∷kanMX4This studyY00891MAT a his3Δ1 leu2Δ0 lys2Δ0 met15Δ0 ura3Δ0 adh2∷kanMX4EUROSCARFbEuropeanS accharomyces cerevisiae Archive for Functional Analysis, Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, D-60439 Frankfurt am Main, Germany.Y06217MAT a his3Δ1 leu2Δ0lys2Δ0 met15Δ0 ura3Δ0 adh3∷kanMX4EUROSCARFbEuropeanS accharomyces cerevisiae Archive for Functional Analysis, Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, D-60439 Frankfurt am Main, Germany.59.2.1MATα leu2 ura3 trp1 met15 lys2 adh4∷kanMX4This studyY03284MAT a his3Δ1 leu2Δ0 met15Δ0 ura3Δ0 adh5∷kanMX4EUROSCARFbEuropeanS accharomyces cerevisiae Archive for Functional Analysis, Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, D-60439 Frankfurt am Main, Germany.900–17-101aMAT a ade2 trp1 ura1 adh1-Δ1 adh2-Δ601 adh3∷TRP1E.T. YoungcBox 357350, Department of Biochemistry, University of Washington, Seattle, WA 98195.60.3.3MAT a trp1 met15Δ-289 adh1-Δ1 adh2-Δ601 adh3∷TRP1 adh4∷kanMX4This study62.3.17MAT a ura3Δ0 met15Δ0 adh1-Δ1 adh2-Δ601 adh3∷TRP1 adh4∷kanMX4 adh5∷kanMX4This studyY03866MAT a his3Δ1 leu2Δ0 met15Δ0 ura3Δ0 sfa1∷kanMX4EUROSCARFbEuropeanS accharomyces cerevisiae Archive for Functional Analysis, Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, D-60439 Frankfurt am Main, Germany.66.1.3MATα his3Δ1 met15 adh1-Δ1 adh2-Δ601 adh3∷TRP1 adh4∷kanMX4 sfa1∷kanMX4YPH499MAT a ura3–52 lys2–801 ade2–101 trp1-Δ63, his3-Δ200 leu2-Δ1D. DelneridSchool of Biological Sciences, University of Manchester, 2,205 Stopford Building, Oxford Road, M13 9PT Manchester, UK.AAD7xMATα ura3–52 lys2–801 ade2–101 trp1-Δ63, his3-Δ200 leu2-Δ1 aad3∷KanMX4 aad4∷KIURA3 aad6∷KanMX4 aad10∷KanMX4 aad14∷KanMX4 aad15∷ScTRP1 DelneridSchool of Biological Sciences, University of Manchester, 2,205 Stopford Building, Oxford Road, M13 9PT Manchester, Department of Cell and Molecular Biology/Microbiology, Göteborg University, Box 462, S-405 30 Göteborg, accharomyces cerevisiae Archive for Functional Analysis, Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität Frankfurt, D-60439 Frankfurt am Main, Box 357350, Department of Biochemistry, University of Washington, Seattle, WA of Biological Sciences, University of Manchester, 2,205 Stopford Building, Oxford Road, M13 9PT Manchester, in a were in a yeast and studies of amino acid catabolism were in containing of yeast 20 of a single and either 20 of ethanol or 20 of for the used or amino acids were from were as required at 20 μg/ml. were in to in a was used to were at 30 NMR were and were identified as (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar). are to in of a at the used The of the alcohol end products of yeast amino acid catabolism were in using as (5Dickinson J.R. Harrison S.J. Dickinson J.A. Hewlins M.J.E. J. Biol. Chem. 2000; 275: 10937-10942Google Scholar). Standard the from to μg/ml. Strain was in yeast for its had of this was ethanol in which leucine was the of and the were then for by which the was corresponding to for this strain in this The of isoamyl alcohol the strain was in the for a the of isoamyl alcohol to of that produced by its parent (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar). the had a in isoamyl alcohol (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar). This that the gene is for of the decarboxylation of acid and that is the minor decarboxylase for of the in leucine the NMR spectrum of a of wild-type strain IWD72 that had been for in a in which was the and was the The was of phenylalanine number of were of in the phenylalanine as a of the of the and of the and and as a of the There were no of that it had all been but the at and were of and of which had been produced from the that was of was of the of 2-phenylethanol at with the at of of 2-phenylethanol, and the at the of that of this were produced from the important identified were of 3-phenylpyruvate and of very at and a one at remain The is very a The latter is of a to in an were to the of and but this was to be the The identified and the that were that in yeast the pathway of phenylalanine catabolism is as shown in in which phenylalanine is first deaminated to The 3-phenylpyruvate is then to which is subsequently to The presence in of can be by the of 3-phenylpyruvate to in an analogous to the conversion of α-ketoisocaproate to and α-ketoisovalerate to which were the catabolism of leucine and valine (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar, J.R. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1998; 273: 25751-25756Google Scholar). the metabolic pathway of phenylalanine catabolism by NMR and to which of the α-ketoacid decarboxylases are a number of were for their ability to grow and 2-phenylethanol in in which phenylalanine was the of the strains were of using phenylalanine as the of and all had by Strain well than all of the other strains carrying mutations have with the wild-type (4Dickinson J.R. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1998; 273: 25751-25756Google Scholar, J.R. D.J. Dawes I.W. Mol. Gen. Scholar). Because the strains to different of the of 2-phenylethanol produced are a than the of in the that a significant in 2-phenylethanol in the The and the single in the of 2-phenylethanol This that the decarboxylation of 3-phenylpyruvate can if any one of the PDC5, PDC6, or is in either or in with any of the other mutations in a of 2-phenylethanol that this open reading frame has no role in the decarboxylation of The that is in dehydrogenase produced wild-type of dehydrogenase is an of branched-chain α-ketoacid pyruvate and decarboxylase M.M. Dickinson J.R. Danner D.J. Mol. 5: Scholar, B. A. Mol. Cell. Biol. 11: Scholar, J.R. D.J. Dawes I.W. Mol. Gen. Scholar, D.A. Dawes I.W. Genetics. Scholar). Hence, strain branched-chain α-ketoacid it can be that this is involved in the formation of 2-phenylethanol from of 2-phenylethanol produced by yeast strains in a with phenylalanine as of these had ethanol as use this strain had as was by each strain had The are the of two between were in a these had ethanol as use this strain had as was by each strain had The are the of two between were the NMR spectrum of a of wild-type strain IWD72 that had been for in a in which was the and was the The two showed to and the NMR spectrum was the as if the tryptophan was of the of tryptophan were as a of the indole at the and in the indole at and at and at in the phenylalanine there were no of that it had all been but the at and and of produced from the were were the at and at of tryptophol, which had been produced from the The at could be The was to be the of S. cerevisiae a of the by the of acids and alcohols J. J. Chem. Scholar). the of tryptophan and ethanol in this the formation of tryptophan would have been a of the spectrum of the showed that it was tryptophan The at is to of 2-phenylethanol and is a that it was of and was from The of this is the identified it is that tryptophan catabolism to tryptophol as shown in The fact that no were of that the of this be its decarboxylation is very This is with the fact that no was the of this be there is no enzyme in yeast that is of to The of used to phenylalanine catabolism were also for their ability to grow and tryptophol in in which tryptophan was the of the strains were of using tryptophan as the of and all except ESH380w had by Strain ESH380w had a very and the final it can be that there were two of The including the in the from to strains and that to for the fact that the strains to different of the of tryptophol produced are a than the in the that of the strains produced of tryptophol to the but strains ESH380w and this Because the and the single of tryptophol, and mutations or in with other in a of tryptophol it is that tryptophan can be catabolized to tryptophol if any one of the genes, PDC6, or is and as with phenylalanine catabolism in this has no of tryptophol and 2-phenylethanol produced by yeast strains in a with tryptophan as of these had ethanol as use this strain had as and 2-phenylethanol were by each strain had The are the of two between were in a these had ethanol as use this strain had as and 2-phenylethanol were by each strain had The are the of two between were were also in the This could be to that dehydrogenase is required for tryptophan catabolism to tryptophol and that there is an metabolic route one or of branched-chain α-ketoacid pyruvate or decarboxylase. we this to be the for three First, the NMR and of the wild-type strain no of or end Second, the any that could be to be from Third, the tryptophol produced by strain is as as in strains ESH380w and a it is of the produced by the wild-type in the We that the tryptophol formation in strain is an of both its and the fact that the of pyruvate dehydrogenase and dehydrogenase will in of which is required in the of The all of the tryptophan by the end of the The NMR of the catabolism of tryptophan the presence of The in Table that were using the presence of 2-phenylethanol at that were between and of the of The of 2-phenylethanol produced by tryptophan as the were about of the produced the were phenylalanine as the This catabolism of phenylalanine yeast is tryptophan as the S. cerevisiae has 20 enzymes that potentially could be involved in the formation of long chain and complex This the putative aryl alcohol dehydrogenases encoded by the family of all of which are of (7Delneri D. Gardner D.C.J. Oliver S.G. Genetics. 1999; 153: 1591-1600Google Scholar, 8Delneri D. Gardner D.C.J. Bruschi C.V. Oliver S.G. Yeast. 1999; 15: 1681-1689Google Scholar), and 13 other alcohol of these can be a of their has been shown recently E. M.R. C. Parés X. Biosca J.A. J. Biol. Chem. 2000; 275: Scholar) to be involved in the formation of the of it is to that can be BDH2 and that it has a SOR2 encode alcohol dehydrogenases A. C. P. 1999; Scholar), which are the of enzyme sought in this CDH1 and ADH6 encode enzymes (9Larroy C. Fernández M.R. González E. Parés X. Biosca J.A. Biochem. J. 2000; 361: 163-172Google Scholar) and are also to be the of enzyme involved This other alcohol of which the first are the is the enzyme involved in the formation of ethanol Adh2p, which is also is the enzyme that is for is it is and its role is work from and B. C. P. J. 2000; Scholar) it is involved in a is at very in but is in strains J.R. Dickinson J.R. The and Molecular of Saccharomyces and Scholar). was by and its role is Sfa1p is of a enzyme that has both dehydrogenase (the gene to which is the of in this it is also as of the of long chain alcohols E. Mol. Gen. Scholar). Hence, each of and Sfa1p has at least one that it could be for the of long chain Adh2p, and all and have known for years that the of in the the of long chain alcohols that are and to be as no role has been to it has been shown that Sfa1p can long chain alcohols in its role in is the formation of these which alcohol dehydrogenase required for the formation of alcohols we used a strain in all seven of its AAD genes and other strains containing all possible combinations of single and mutations affecting the alcohol These strains were then in containing a single amino acid as the and for the ability to the alcohol end corresponding to the amino acid the of isoamyl alcohol produced a of these strains were leucine as the of the strains produced isoamyl were using other combinations of mutations and different single amino acid It that the AAD genes have no role in long chain or complex alcohol formation. Using both and by to strains carrying alcohol dehydrogenase it to a haploid that had mutations in all alcohol dehydrogenase this we that as long as yeast has one enzyme of or Sfa1p that is it is and to long chain and complex of isoamyl alcohol produced by yeast strains in with leucine as of alcohol was by each strain had The are the of two between were in a alcohol was by each strain had The are the of two between were of leucine catabolism had identified Ydl080cp as the major of this open reading frame to an of the formation of isoamyl alcohol (3Dickinson J.R. Lanterman M.M. Danner D.J. Pearson B.M. Sanz P. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1997; 272: 26871-26878Google Scholar). The has identified Ydr380wp as the minor decarboxylase for of the both and YDR380w are a haploid strain of S. cerevisiae in with leucine as the no isoamyl alcohol that no other pathway for the of this This has shown that in S. cerevisiae the catabolism of phenylalanine to 2-phenylethanol and of tryptophan to tryptophol are both accomplished in a way corresponding to has been the pathway (1Webb A.D. Ingraham J.L. Adv. Appl. Microbiol. 1963; 5: 317-353Google Scholar). from studies in different yeast it is Yeast. Scholar) that phenylalanine to and and that the is subsequently to which is then to The that tryptophan degradation by a to is to which then has an to The pathway subsequently and for both pathways S. J. 138: Scholar, S. J. Scholar). NMR showed no of any of the of either of these the end of both phenylalanine and tryptophan would a in the of the There was no in either The possible is that cerevisiae phenylalanine and tryptophan are catabolized to the pathway. In both phenylalanine and tryptophan catabolism the decarboxylation step is by any one of the gene products of PDC6, or has no in the catabolism of either of these amino it is that in each of the amino acid catabolic pathways that we have the decarboxylation step is accomplished in subtly different In leucine catabolism Ydl080cp is the major and Ydr380wp is the minor decarboxylase. In valine catabolism any one of the pyruvate decarboxylase isozymes Pdc5p, or can the decarboxylation of α-ketoisovaleric acid (4Dickinson J.R. Harrison S.J. Hewlins M.J.E. J. Biol. Chem. 1998; 273: 25751-25756Google Scholar), in isoleucine catabolism any one of the five-membered family of decarboxylases Pdc5p, Pdc6p, Ydl080cp, or is In for catabolism of the aromatic amino acids phenylalanine and tryptophan is it is for these two This showed that any one of alcohol dehydrogenases by ADH3, or is sufficient for the final stage of long chain or complex alcohol formation in S. this that alcohol dehydrogenase will and alcohols all an will grow in of the alcohol dehydrogenase is by than years well the and of this yeast were it had been that the final step in alcohol formation was by either of the enzymes that are known as or S. Biochem. J. Scholar). This but was a of all of the alcohol dehydrogenases that yeast The of the seven AAD genes remain In S. cerevisiae catabolism of the three branched-chain amino acids valine, and and the two aromatic amino acids and as proposed years F. Chem. Scholar). it is complex than yeast at least three and alcohol The of enzymes used at a the amino the and the stage of of the In our the major with the It is the of these decarboxylases that is the of our