Growth on Alpha-Ketoglutarate Increases Oxidative Stress Resistance in the Yeast Saccharomyces cerevisiae

Abstract

Alpha-ketoglutarate (AKG) is an important intermediate in cell metabolism, linking anabolic and catabolic processes. The effect of exogenous AKG on stress resistance in S. cerevisiae cells was studied. The growth on AKG increased resistance of yeast cells to stresses, but the effects depended on AKG concentration and type of stressor. Wild-type yeast cells grown on AKG were more resistant to hydrogen peroxide, menadione, and transition metal ions (Fe²⁺ and Cu²⁺) but not to ethanol and heat stress as compared with control ones. Deficiency in SODs or catalases abolished stress-protective effects of AKG. AKG-supplemented growth led to higher values of total metabolic activity, level of low-molecular mass thiols, and activities of catalase and glutathione reductase in wild-type cells compared with the control. The results suggest that exogenous AKG may enhance cell metabolism leading to induction of mild oxidative stress. It turn, it results in activation of antioxidant system that increases resistance of S. cerevisiae cells to H₂O₂ and other stresses. The presence of genes encoding SODs or catalases is required for the expression of protective effects of AKG.

Figure 1

Growth curves of S. cerevisiae YPH250 in YPD medium in the presence of AKG at different concentrations. Growth was monitored by measuring the absorbance at 620 nm (OD₆₂₀).

Figure 2

Effect of exposure to 10 mM H₂O₂ for 30 min on cell survival in S. cerevisiae YPH250 strain and its isogenic derivatives grown in the absence or presence of 10 mM AKG. (a) YPH250 cells (wild type) grown with AKG different concentrations; (b) mutant cells grown without or with 10 mM AKG; (c) Δcta1Δctt1 cells grown without or with AKG and were treated with only 10 mM H₂O₂ denoted as “control” and “AKG (growth),” respectively; “AKG (incubation),” Δcta1Δctt1 cells grown without AKG were treated with 10 mM H₂O₂ in combination with 10 mM AKG. Data are means ± SEM, n = 5-6. ^∗Significantly different from respective control values with P < 0.05 using Dunnett's test (a) or Student's t-test (b, c).

Figure 3

Effect of exposure to 10 mM H₂O₂ for 30 min on catalase activity (a) and level of protein carbonyls (b) in S. cerevisiae YPH250 cells grown in the absence or presence of 10 mM AKG. Untreated cells (without H₂O₂) and cells treated with 10 mM H₂O₂ are marked by white square and grey square bars, respectively. Data are means ± SEM, n = 5-6. ^∗Significantly different from respective values of untreated cells and ^#from respective values of control group (without AKG) with P < 0.05 using Student's t-test, n = 5-6.

Figure 4

Native PAGE electrophoresis of catalase isoforms in S. cerevisiae YPH250 cells grown in the absence or presence of 10 mM AKG. An amount of total protein applied to each well was 10 µg.