title: Ascorbate abolishes auxotrophy caused by the lack of superoxide dismutase in Saccharomyces cerevisiae. Yeast can be a biosensor for antioxidants.
abstract: Yeast (Saccharomyces cerevisiae) mutants lacking cytoplasmic superoxide dismutase (CuZnSOD) show Lys and Met auxotrophy under aerobic conditions. This metabolic defect can be ameliorated by exogenous ascorbate as well as other antioxidants (glutathione, cysteine and N-acetylcysteine). Restoration of growth of CuZnSOD- yeast mutants on media devoid of Met and/or Lys may therefore be a simple and useful means to detect and quantify antioxidants. The protective effect of antioxidants is oxygen-dependent: the lower the oxygen content of the atmosphere, the lower antioxidant concentrations are required to restore prototrophy. Therefore, the sensitivity of the test can be augmented by growing the yeast under lowered partial oxygen pressure. While 6 mM, 10 mM and 30 mM ascorbate was necessary to restore the growth in the absence of Met, in the absence of Lys, and in the absence of Lys and Met, respectively, under 21% oxygen, 3 mM and 6 mM ascorbate was sufficient for growth restoration in the absence of Lys and in the absence of Lys and Met, respectively, under 3% oxygen. The protective effects of cysteine and N-acetylcysteine peaked at 0.5 mM and 6 mM, respectively, disappearing at higher concentrations of these compounds, pointing to the detection of not only protective but also toxic cellular effects of the compounds studied by the test proposed.
authors.affiliation: University of Rzeszów, ul. Rejtana 16, PL 35-310 Rzeszów, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Zyracka
authors.forename: Renata
authors.initials: R
authors.lastname: Zadrag
authors.forename: Sabina
authors.initials: S
authors.lastname: Kozioł
authors.forename: Anna
authors.initials: A
authors.lastname: Krzepiłko
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bartosz
authors.forename: Tomasz
authors.initials: T
authors.lastname: Biliński
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage* / Q000032:analysis; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000032:analysis; D015374:Biosensing Techniques / Q000379:methods*; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D013482:Superoxide Dismutase / Q000172:deficiency*
chemical_list: D000975:Antioxidants; D013482:Superoxide Dismutase; D001205:Ascorbic Acid; D010100:Oxygen