title: Aerobic physiology of redox-engineered Saccharomyces cerevisiae strains modified in the ammonium assimilation for increased NADPH availability.
abstract: Recombinant strains altered in the ammonium assimilation pathways were constructed with the purpose of increasing NADPH availability. The NADPH-dependent glutamate dehydrogenase encoded by GDH1, which accounts for a major fraction of the NADPH consumption during growth on ammonium, was deleted, and alternative pathways for ammonium assimilation were overexpressed: GDH2 (NADH-consuming) or GLN1 and GLT1 (the GS-GOGAT system). The flux through the pentose phosphate pathway during aerobic growth on glucose decreased to about half that of the reference strain Saccharomyces cerevisiae CEN.PK113-7D, indicating a major redox alteration in the strains. The basic growth characteristics of the recombinant strains were not affected to a great extent, but the dilution rate at which the onset of aerobic fermentation occurred decreased, suggesting a relation between the onset of the Crabtree effect and the flux through the Embden-Meyerhof-Parnas pathway downstream of glucose 6-phosphate. No redox effect was observed in a strain containing a deletion of GLR1, encoding glutathione reductase, an enzyme that is NADPH-consuming.
authors.affiliation: Center for Process Biotechnology, BioCentrum-DTU, Building 223, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Margarida
authors.initials: M
authors.lastname: Moreira dos Santos
authors.forename: Gerda
authors.initials: G
authors.lastname: Thygesen
authors.forename: Peter
authors.initials: P
authors.lastname: Kötter
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Olsson
authors.forename: Jens
authors.initials: J
authors.lastname: Nielsen
mesh_terms: D000332:Aerobiosis; D000641:Ammonia / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D005800:Genes, Fungal; D005818:Genetic Engineering; D006019:Glycolysis; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D009249:NADP; D000641:Ammonia