title: Pyruvate kinase (Pyk1) levels influence both the rate and direction of carbon flux in yeast under fermentative conditions.
abstract: Yeast phosphofructo-1-kinase (Pf1k) and pyruvate kinase (Pyk1) are allosterically regulated enzymes that catalyse essentially irreversible reactions in glycolysis. Both the synthesis and activity of these enzymes are tightly regulated. To separate experimentally the control of Pf1k and Pyk1 synthesis from their allosteric regulation, a congenic set of PFK1, PFK2 and PYK1 mutants was constructed in which these wild-type coding regions were driven by alternative promoters. Mutants carrying PGK1 promoter fusions displayed normal rates of growth, glucose consumption and ethanol production, indicating that the relatively tight regulation of Pyk1 and Pf1k synthesis is not essential for glycolytic control under fermentative growth conditions. Mutants carrying fusions to an enhancer-less version of the PGK1 promoter (PGK1(Delta767)) expressed Pyk1 and Pf1k at about 2.5-fold lower levels than normal. Physiological and metabolic analysis of the PFK1 PFK2 double mutant indicated that decreased Pf1k had no significant effect on growth, apparently due to compensatory increases in its positive effector, fructose 2,6-bisphosphate. In contrast, growth rate and glycolytic flux were reduced in the PGK1(Delta767)-PYK1 mutant, which had decreased Pyk1 levels. Unexpectedly, the reduced Pyk1 levels caused the flow of carbon to the TCA cycle to increase, even under fermentative growth conditions. Therefore, Pyk1 exerts a significant level of control over both the rate and direction of carbon flux in yeast.
authors.affiliation: Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Pearce
authors.affiliation: Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1.
authors.forename: Kay
authors.initials: K
authors.lastname: Crimmins
authors.affiliation: Centre de Bioingenierie Gilbert Durand, UMR-CNRS 5504 UR-INRA 792, Département de Génie Biochimique et Alimentaire, Institut National des Sciences Appliquées, 31077 Toulouse Cedex 04, France2.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Groussac
authors.affiliation: Department of Chemistry, Cardiff University, PO Box 912, Cardiff CF10 3TB, UK3.
authors.forename: Michael J E
authors.initials: MJE
authors.lastname: Hewlins
authors.affiliation: Cardiff School of Biosciences, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK4.
authors.forename: J Richard
authors.initials: JR
authors.lastname: Dickinson
authors.affiliation: Centre de Bioingenierie Gilbert Durand, UMR-CNRS 5504 UR-INRA 792, Département de Génie Biochimique et Alimentaire, Institut National des Sciences Appliquées, 31077 Toulouse Cedex 04, France2.
authors.forename: Jean
authors.initials: J
authors.lastname: Francois
authors.affiliation: Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Booth
authors.affiliation: Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1.
authors.forename: Alistair J P
authors.initials: AJP
authors.lastname: Brown
mesh_terms: D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D006019:Glycolysis; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D010732:Phosphofructokinase-1 / Q000235:genetics / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D010732:Phosphofructokinase-1; D011770:Pyruvate Kinase