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Copper-zinc superoxide dismutase (Cu,Zn-SOD) and manganese superoxide dismutase (Mn-SOD) in some model experiments in vitro demonstrated antioxidant as well as pro-oxidant properties. In the present study, yeast Saccharomyces cerevisiae lacking Mn-SOD were studied using Cu,Zn-SOD inhibitor N-N′-diethyldithiocarbamate (DDC) as a model system to study the physiological role of the yeast Cu,Zn-SOD. Yeast treatment by DDC caused dose-dependent inhibition of SOD in vivo, with 75% inhibition at 10mM DDC. The inhibition of SOD by DDC resulted in modification of carbonylprotein levels, indicated by a bell-shaped curve. The activity of glutathione reductase, isocitrate dehydrogenase, and glucose-6-phosphate dehydrogenase (enzymes associated with antioxidant) increased, demonstrating a compensatory effect in response to SOD inhibition by different concentrations of DDC. A strong positive …