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The supression by natural antioxidants of oxygen sensitivity in yeast strains lacking mitrochondrial and cytoplasmic superoxide dismutases

We prepared three Saccharomyces cerevisiae strains deficient in superoxide dismutases, one lacking cytoplasmic Cu,Zn-superoxide dismutase (∆sod1), one lacking mitochondrial Mn-superoxide dismutase (∆sod2), and the third, a double mutant lacking the genes for both (∆sod1∆sod2). Study of the growth of these strains in the presence and absence of oxygen or paraquat (a superoxide radical generating agent) showed that strain ∆sod1 exhibited an increased sensitivity to oxygen and paraquat relative to the SOD-competent controls. Deletion of the sod2 gene did not change the strain's sensitivity to oxygen and paraquat when the yeast was grown anaereobically. However, this strain revealed sensitivity to paraquat when grown in the presence of oxygen. The double mutant had the phenotype of the ∆sod1 strain. Different concentrations of four compounds (β-carotene, quercetin, vitamins A and E) were tested for their suppressor action on the ∆sod1, ∆sod2 and ∆sod1∆sod2 strains. Quercetin showed strong suppression of the oxygen sensitivity of ∆sod1 and the double deleted strain at 25 and 100 µM. At 1 and 25 µM, vitamin A also stimulated the growth of the investigated strains. Under our experimental conditions, the impacts of β-carotene and vitamin E was not significant.