Expression of human Cn, Zn-superoxide dismutase in escherichia coli

Superoxide dismutase (SOD) is the enzyme that catalyzes the disproportionation or dismutation of superoxide radical (O_2^-) . It plays an important role to defend against oxidative damage mediated by O_2^-. Recombinant DNA was constructed for the expression of the human Cu, Zn -SOD cDNA. It is designed to express directly the secombinant SOD (rSOD) under the control of colicin E_1 gene regulatory elements in Escherichia coli. Expression of rSOD was regulated in the same way as the original ColE_1 plasmid with respect to the repressibility and inducibility. The enzyme was purified by heat treatment, salt precipitation, ion echange chromatography and gel filtration chromatography. Edman degradation of rSOD revealed that the N-terminal was not methionine, but alanine which was not acetylated. rSOD had an activity comparable to the human erythrocyte enzyme. E. coli cells bearing the recombinant plasmid produced rSOD in more than 10% of the total becteroal protein.