title: Determination of the Cytosolic NADPH/NADP Ratio in Saccharomyces cerevisiae using Shikimate Dehydrogenase as Sensor Reaction.
abstract: Eukaryotic metabolism is organised in complex networks of enzyme catalysed reactions which are distributed over different organelles. To quantify the compartmentalised reactions, quantitative measurements of relevant physiological variables in different compartments are needed, especially of cofactors. NADP(H) are critical components in cellular redox metabolism. Currently, available metabolite measurement methods allow whole cell measurements. Here a metabolite sensor based on a fast equilibrium reaction is introduced to monitor the cytosolic NADPH/NADP ratio in Saccharomyces cerevisiae: NADP + shikimate ⇄ NADPH + H(+) + dehydroshikimate. The cytosolic NADPH/NADP ratio was determined by measuring the shikimate and dehydroshikimate concentrations (by GC-MS/MS). The cytosolic NADPH/NADP ratio was determined under batch and chemostat (aerobic, glucose-limited, D = 0.1 h(-1)) conditions, to be 22.0 ± 2.6 and 15.6 ± 0.6, respectively. These ratios were much higher than the whole cell NADPH/NADP ratio (1.05 ± 0.08). In response to a glucose pulse, the cytosolic NADPH/NADP ratio first increased very rapidly and restored the steady state ratio after 3 minutes. In contrast to this dynamic observation, the whole cell NADPH/NADP ratio remained nearly constant. The novel cytosol NADPH/NADP measurements provide new insights into the thermodynamic driving forces for NADP(H)-dependent reactions, like amino acid synthesis, product pathways like fatty acid production or the mevalonate pathway.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Jinrui
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Angela
authors.initials: A
authors.lastname: ten Pierick
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Harmen M
authors.initials: HM
authors.lastname: van Rossum
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Reza Maleki
authors.initials: RM
authors.lastname: Seifar
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Cor
authors.initials: C
authors.lastname: Ras
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Daran
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Heijnen
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, 2628BC, The Netherlands.
authors.forename: S Aljoscha
authors.initials: SA
authors.lastname: Wahl
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry*; D015374:Biosensing Techniques; D050260:Carbohydrate Metabolism; D003593:Cytoplasm / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D007700:Kinetics; D064688:Metabolic Flux Analysis; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D009249:NADP; D000429:Alcohol Oxidoreductases; C022641:Shikimate dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D005947:Glucose