title: A 13C nuclear magnetic resonance investigation of the metabolism of leucine to isoamyl alcohol in Saccharomyces cerevisiae.
abstract: The metabolism of leucine to isoamyl alcohol in yeast was examined by 13C nuclear magnetic resonance spectroscopy. The product of leucine transamination, alpha-ketoisocaproate had four potential routes to isoamyl alcohol. The first, via branched-chain alpha-keto acid dehydrogenase to isovaleryl-CoA with subsequent conversion to isovalerate by acyl-CoA hydrolase operates in wild-type cells where isovalerate appears to be an end product. This pathway is not required for the synthesis of isoamyl alcohol because abolition of branched-chain alpha-keto acid dehydrogenase activity in an lpd1 disruption mutant did not prevent the formation of isoamyl alcohol. A second possible route was via pyruvate decarboxylase; however, elimination of pyruvate decarboxylase activity in a pdc1 pdc5 pdc6 triple mutant did not decrease the levels of isoamyl alcohol produced. A third route utilizes alpha-ketoisocaproate reductase (a novel activity in Saccharomyces cerevisiae) but with no role in the formation of isoamyl alcohol from alpha-hydroxyisocaproate because cell homogenates could not convert alpha-hydroxyisocaproate to isoamyl alcohol. The final possibility was that a pyruvate decarboxylase-like enzyme encoded by YDL080c appears to be the major route of decarboxylation of alpha-ketoisocaproate to isoamyl alcohol although disruption of this gene reveals that at least one other unidentified decarboxylase can substitute to a minor extent.
authors.affiliation: School of Pure & Applied Biology, University of Wales, Cardiff CF1 3TL, United Kingdom.
authors.forename: J R
authors.initials: JR
authors.lastname: Dickinson
authors.forename: M M
authors.initials: MM
authors.lastname: Lanterman
authors.forename: D J
authors.initials: DJ
authors.lastname: Danner
authors.forename: B M
authors.initials: BM
authors.lastname: Pearson
authors.forename: P
authors.initials: P
authors.lastname: Sanz
authors.forename: S J
authors.initials: SJ
authors.lastname: Harrison
authors.forename: M J
authors.initials: MJ
authors.lastname: Hewlins
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000214:Acyl Coenzyme A / Q000378:metabolism; D000595:Amino Acid Sequence; D002247:Carbon Isotopes; D016384:Consensus Sequence; D005800:Genes, Fungal; D005838:Genotype; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism; D000439:Pentanols / Q000378:metabolism*; D011767:Pyruvate Decarboxylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013869:Thiolester Hydrolases / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D002247:Carbon Isotopes; D007527:Isoenzymes; D009097:Multienzyme Complexes; D000439:Pentanols; C017447:isovaleryl-coenzyme A; C029683:isopentyl alcohol; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D013869:Thiolester Hydrolases; D011767:Pyruvate Decarboxylase; D007930:Leucine