EFFECTS OF BICARBONATE AND ALPHA-KETOGLUTARATE ON SENSITIVITY OF SACCHAROMYCES CEREVISIAE YEAST TO HYDROGEN PEROXIDE AND IRON IONS

Abstract

The effects of sodium bicarbonate on the sensitivity of Saccharomyces cerevisiae yeast to hydrogen peroxide and ferrous sulfate were studied. Viability of yeast cells treated with 10–25 mM H₂O₂ and 0.1–0.2 mM FeSO₄ was significantly decreased when 25 or 50 mM NaHCO₃ was added to the medium. In the absence of bicarbonate, the levels of oxidative stress markers, namely protein carbonyls, total and oxidized glutathione in cells exposed to 0.2 mM FeSO₄ did not differ from such levels in control cells (without FeSO₄). Yeast cells incubated with 0.2 mM FeSO₄ and 50 mM NaHCO₃ had similar levels of oxidized glutathione and carbonyl groups in proteins but lower level of total glutathione compared to cells treated with FeSO₄ in the absence of NaHCO₃. Yeast cells exposed to a mixture of “2 mM H₂O₂ + 2 mM FeSO₄” in 50 mM sodium bicarbonate buffer survived better than cells treated with these oxidants in 50 mM potassium phosphate buffer. The addition of 10 mM alpha-ketoglutarate led to the increased yeast survival in both buffers under the treatment with “Fe²⁺/Н₂О₂”. The protective effect of alpha-ketoglutarate can be due to its H₂O₂-scavenging activity. The results suggest that bicarbonate ions can enhance or alleviate the toxic effects of redox-active compounds on S. cerevisiae. Pro/antioxidant effects of bicarbonate ions are likely to depend on the kinetics of interaction between HCO₃ˉ and produced ROS.