title: Nonstatistical 13C distribution during carbon transfer from glucose to ethanol during fermentation is determined by the catabolic pathway exploited.
abstract: During the anaerobic fermentation of glucose to ethanol, the three micro-organisms Saccharomyces cerevisiae, Zymomonas mobilis, and Leuconostoc mesenteroides exploit, respectively, the Embden-Meyerhof-Parnas, the Entner-Doudoroff, and the reductive pentose phosphate pathways. Thus, the atoms incorporated into ethanol do not have the same affiliation to the atomic positions in glucose. The isotopic fractionation occurring in each pathway at both the methylene and methyl positions of ethanol has been investigated by isotopic quantitative (13)C NMR spectrometry with the aim of observing whether an isotope redistribution characteristic of the enzymes active in each pathway can be measured. First, it is found that each pathway has a unique isotope redistribution signature. Second, for the methylene group, a significant apparent kinetic isotope effect is only found in the reductive pentose phosphate pathway. Third, the apparent kinetic isotope effects related to the methyl group are more pronounced than for the methylene group. These findings can (i) be related to known kinetic isotope effects of some of the enzymes concerned and (ii) give indicators as to which steps in the pathways are likely to be influencing the final isotopic composition in the ethanol.
authors.affiliation: From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France.
authors.forename: Kevin
authors.initials: K
authors.lastname: Bayle
authors.affiliation: From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France.
authors.forename: Serge
authors.initials: S
authors.lastname: Akoka
authors.affiliation: From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France.
authors.forename: Gérald S
authors.initials: GS
authors.lastname: Remaud
authors.affiliation: From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France richard.robins@univ-nantes.fr.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Robins
mesh_terms: D002250:Carbon Radioisotopes / Q000493:pharmacokinetics*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D007934:Leuconostoc / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D010427:Pentose Phosphate Pathway; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014018:Tissue Distribution; D017355:Zymomonas / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D000431:Ethanol; D005947:Glucose
keywords: 13C NMR; Alcohol; Carbohydrate Metabolism; Glucose Metabolism; Isotope Effect; Isotopic Fractionation; Leuconostoc mesenteroides; Saccharomyces cerevisiae; Zymomonas mobilis