Escherichia coli subsp. expressing AmSOD

The SOD activity of His-AmSOD1 which was produced in the medium containing both copper and zinc was determined after incubation of enzyme at different temperature for 1 h (Fig. 5A). About 80% of SOD activity was remained after 1 h incubation of AmSOD at temperatures 25, 35 and 50◦C. The T1/2(reduction in activity to 50%) of AmSOD was

3.9. Tolerance of E. coli expressing AmSOD 1 to salt and hydrogen

peroxide

The comparison of growth curves of strain R-AmSOD and control reveals that in the medium with no treatment, the maximum O.D.600 (OD 600 after 10.5 h) for R-AmSOD is almost similar to control strain (1.8 ± 0.1 versus 1.7 ± 0.08)rsus 1.7. In the presence of 600 mM NaCl the maximum O.D. 600 for both strains significantly decreased and reached to about 1.3. The same amount of reduction for both strains suggests that the heterologus expression of AmSOD1 does not affect on the tolerance of E. coli to NaCL. Furthermore the hydrogen peroxide tolerance of strains was analyzed using growth curve. In the presence of 8 mM H 2 O 2 the maximum OD for control strain significantly (P <0.01) decreased and reached to 1.17. However the maximum OD for R-AmSOD1 did not change and remained constant, suggesting the role of AmSOD 1 in the tolerance of E. coli to hydrogen peroxide (Fig. 7).