title: Metabolic-flux profiling of the yeasts Saccharomyces cerevisiae and Pichia stipitis.
abstract: The so far largely uncharacterized central carbon metabolism of the yeast Pichia stipitis was explored in batch and glucose-limited chemostat cultures using metabolic-flux ratio analysis by nuclear magnetic resonance. The concomitantly characterized network of active metabolic pathways was compared to those identified in Saccharomyces cerevisiae, which led to the following conclusions. (i) There is a remarkably low use of the non-oxidative pentose phosphate (PP) pathway for glucose catabolism in S. cerevisiae when compared to P. stipitis batch cultures. (ii) Metabolism of P. stipitis batch cultures is fully respirative, which contrasts with the predominantly respiro-fermentative metabolic state of S. cerevisiae. (iii) Glucose catabolism in chemostat cultures of both yeasts is primarily oxidative. (iv) In both yeasts there is significant in vivo malic enzyme activity during growth on glucose. (v) The amino acid biosynthesis pathways are identical in both yeasts. The present investigation thus demonstrates the power of metabolic-flux ratio analysis for comparative profiling of central carbon metabolism in lower eukaryotes. Although not used for glucose catabolism in batch culture, we demonstrate that the PP pathway in S. cerevisiae has a generally high catabolic capacity by overexpressing the Escherichia coli transhydrogenase UdhA in phosphoglucose isomerase-deficient S. cerevisiae.
authors.affiliation: Institute of Molecular Biology and Biophysics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Fiaux
authors.forename: Z Petek
authors.initials: ZP
authors.lastname: Cakar
authors.forename: Marco
authors.initials: M
authors.lastname: Sonderegger
authors.forename: Kurt
authors.initials: K
authors.lastname: Wüthrich
authors.forename: Thomas
authors.initials: T
authors.lastname: Szyperski
authors.forename: Uwe
authors.initials: U
authors.lastname: Sauer
mesh_terms: D000596:Amino Acids / Q000096:biosynthesis; D000746:Anemia, Hemolytic, Congenital Nonspherocytic; D019069:Cell Respiration / Q000502:physiology; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000502:physiology*; D005285:Fermentation / Q000502:physiology; D005947:Glucose / Q000172:deficiency*; D005956:Glucose-6-Phosphate Isomerase / Q000235:genetics; D008293:Malates / Q000378:metabolism; D009250:NADP Transhydrogenases / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010427:Pentose Phosphate Pathway / Q000502:physiology; D010843:Pichia / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D008293:Malates; C030298:malic acid; D009250:NADP Transhydrogenases; D005956:Glucose-6-Phosphate Isomerase; D005947:Glucose