EFFECT OF CD2+ ON THE ANTIOXIDANT STATUS OF SHIZOSACCHAROMYCES POMBE

The influence of Cd2+ on the antioxidant system of Shizosaccharomyces pombe DSMZ 70576 was studied during batch cultivation on YPD medium containing 1.0 mM Cd(NO3)(2) versus a control variant without Cd(NO3)(2). The Cd2+ was added to the medium on the 12th h of the process. Samples for determination of the cells' growth, carbon source consumption, ethanol production and antioxidant system's status, represented by the enzymes superoxide dismutase (SOD) and catalase (CAT), and the intracellular principal antioxidant glutathione, were taken along the 48 h cultivation. The presence of 1.0 mM Cd2+ under the test conditions repressed the cell growth and resulted in less production of ethanol. The SOD and CAT specific enzyme activities and glutathione concentration were estimated as 11.8 U mg(-1), 1.7 U mg(-1) and 0.57 mM mg(-1) respectively. The SOD and glutathione values were 1,6 and 1.7 fold higher than the corresponding ones measured during growth without Cd2+, while the CAT activity decreased by 40%. These results indicate that glutathione obviously had scavenged efficiently the H2O2 produced, thus compensated the diminished CAT activity and probably maintained the H2O2 homeostasis of the culture under the stress conditions. Electrophoretical analysis of SOD and CAT in cell free extracts obtained from the strain cultivated in the presence of Cd2+ and in norma indicated the absence of Mn SOD enzyme under the stress conditions. Apparently, the presence of 1.0 mM Cd(NO3)(2) leaded to inhibition of mitochondrial functions and Mn SOD operation in the cells of Shizosaccharomyces pombe.