title: α,β-Dicarbonyl reduction is mediated by the Saccharomyces Old Yellow Enzyme.
abstract: The undesirable flavor compounds diacetyl and 2,3-pentanedione are vicinal diketones (VDKs) formed by extracellular oxidative decarboxylation of intermediate metabolites of the isoleucine, leucine and valine (ILV) biosynthetic pathway. These VDKs are taken up by Saccharomyces and enzymatically converted to acetoin and 3-hydroxy-2-pentanone, respectively. Purification of a highly enriched diacetyl reductase fraction from Saccharomyces cerevisiae in conjunction with mass spectrometry identified Old Yellow Enzyme (Oye) as an enzyme capable of catalyzing VDK reduction. Kinetic analysis of recombinant Oye1p, Oye2p and Oye3p isoforms confirmed that all three isoforms reduced diacetyl and 2,3-pentanedione in an NADPH-dependent reaction. Transcriptomic analysis of S. cerevisiae (ale) and S. pastorianus (lager) yeast during industrial fermentations showed that the transcripts for OYE1, OYE2, arabinose dehydrogenase (ARA1), α-acetolactate synthase (ILV2) and α-acetohydroxyacid reductoisomerase (ILV5) were differentially regulated in a manner that correlated with changes in extracellular levels of VDKs. These studies provide insights into the mechanism for reducing VDKs and decreasing maturation times of beer which are of commercial importance.
authors.affiliation: Department of Bioresource Engineering, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.
authors.forename: Barry
authors.initials: B
authors.lastname: van Bergen
authors.affiliation: Institute of Parasitology, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC 27612, USA.
authors.forename: Normand
authors.initials: N
authors.lastname: Cyr
authors.affiliation: Institute of Parasitology, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.
authors.forename: Rona
authors.initials: R
authors.lastname: Strasser
authors.affiliation: Department of Bioresource Engineering, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Blanchette
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC 27612, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Sheppard
authors.affiliation: Institute of Parasitology, Macdonald Campus of McGill University, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada armando.jardim@mcgill.ca.
authors.forename: Armando
authors.initials: A
authors.lastname: Jardim
mesh_terms: D000093:Acetoin / Q000378:metabolism; D003931:Diacetyl / Q000378:metabolism*; D020869:Gene Expression Profiling; D007700:Kinetics; D013058:Mass Spectrometry; D009249:NADP / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D010422:Pentanones / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism*
chemical_list: D010422:Pentanones; D009249:NADP; D000093:Acetoin; C004395:acetylethylcarbinol; D009252:NADPH Dehydrogenase; D003931:Diacetyl; C013186:2,3-pentanedione
keywords: 2,3-butanedione; Old Yellow Enzyme; Saccharomyces α,β-dicarbonyl; diacetyl