SOD and Catalase Induction on Saccharomyces cerevisiae strains by Heavy Metals and methanol

The tolerance that yeasts have shown to high concentrations of copper has prompted several studies of the effects of copper addition on copper-containing enzymes of yeasts. The metabolic alteration caused by copper may result, in turn, in an adaptive increase of anti oxidative enzymes. Cu,ZnSOD in yeats appear particularly sensitive to extremes of the environmental [CU]. methanol also resulted as an inductor of SOD activity in yeasts; this enzyme is responsible for the disputation of =2- that together with H2O2 (dismutated by catalase) and OH are known for their toxicity and destructive power toward living cells. SOD and catalase lower the concentrations of O2 and H2O2 respectively minimizing the generation of OH. But it is not clear if a direct correlation between SOD and catalase increases exists. To check the growth rate and SOD and catalase levels of these yeast cultures we used the addition of copper and cadmim in a basal medium for yeast growth and the association of methanol to these media. Saccharomyces cerevisiae strains SS1090 and SS1189 were grown on Malt Extract Broth with the addition of copper at 320 μM final value or cadmium at 40 μM final value and on Malt Extract Broth (Oxoid) for the blank. At the same substrata was then added methanol at 1.5% (v/v) (Prolabo). Metal and methanol were sterilized by filtration using Sartorius membrane 0.2 μM pore sizes. Cells made active were inoculated in 100 ml of culture media and were incubated at 30°C in a water bath vigorously shaken for 48 hours. Cells counts using a haematocytometer at an 8 hours interval were made to obtain the growth rate. Cell extract, obtained by breaking with glass beads was dialyzed in buffer solution overnight for the determination of enzymatic and protein concentration. The protein content was determined with the method of Lowry modified by Peterson. For the SOD activity determination a modification of the indirect method proposed by Puget & Michelson was used. For the determination of catalase activity the method of Michelson et al. was used. We noted that the addition of methanol at 1.5% (v/v) to the media (with or without copper) did not have detectable effects on growth rate. On the other hand the conjunction of cadmium and methanol caused a noticeable effect on growth rate of eighter the strains used in the test. The analyses of SOD and catalase level showed that there was no correlation between SOD and catalase. However, SOD activity is always higher in strains grown on copper than in strains grown on cadmium or the blank. The increase of SOD independently from catalase increase and viceversa, when submitted to metal and alcohol stressing tests, which leads us to think that there is no correlation between SOD and catalase activity.