ABSTRACT
Deficiencies in superoxide dismutases (Cu,ZnSOD or Mn-SOD) strongly shorten the life span of yeast cells. The effects of these deficiencies are additive. In contrast, deficiencies in catalases do not influence life span. Our results confirm that free radical processes may be involved in aging.
Subject(s)
Saccharomyces cerevisiae/cytology , Saccharomyces cerevisiae/enzymology , Superoxide Dismutase/metabolismABSTRACT
It has been found that yeast mutants deficient in cytosolic superoxide dismutase CuZnSOD are hypersensitive to ferrous iron. In contrast mutants that are deficient in catalases and cytochrome c peroxidase do not differ from the standard strain in this respect. These findings suggest that iron toxicity may depend on the redox status of the cell. They also shed light on the role of superoxide dismutases in preventing the toxic effects of oxygen.
Subject(s)
Iron/toxicity , Superoxide Dismutase/physiology , Yeasts/physiology , Acatalasia , Cell Division/drug effects , Cell Division/genetics , Cytochrome-c Peroxidase/deficiency , Hydrogen Peroxide/metabolism , Iron/pharmacokinetics , Mutation , Oxygen/toxicityABSTRACT
It has been found that yeast cells are sensitive to iron overload only when grown on glucose as a carbon source. Effective concentration of ferrous iron is much higher than that found in natural environments. Effects of ferrous iron are strictly oxygen dependent, what suggest that the formation of hydroxyl radicals in the Fenton reaction is a cause of the toxicity. Respiratory deficiency and pretreatment of cells with antimycin A prevent toxic effects in the late exponential phase of growth, whereas uncouplers and 2mM magnesium salts completely protect even the most vulnerable exponential cells. Generally, toxic effects correlate with the ability of cells to take up this metal. The results presented suggest that during ferrous iron overload iron is transported through the unspecific divalent cation uptake system which is known in fungi. The data suggest that recently described high and low affinity systems of iron uptake in yeast are the only source of iron in natural environments.
