Expression, purification and characterisation of human copper-zinc superoxide dismutase protein and human-escherichia coli copper-zinc superoxide dismutase chimeric protein

Abstract

Superoxide dismutases (SODs) represent the first line of defense to counter oxidative stress caused by superoxide radicals, O2˙¯, these being the initial reduction products of oxygen, by catalysing their dismutation into O2 and H2O2. The latter is further decomposed by peroxidases and catalases. CuZn SOD has been considered as being almost exclusively a dimeric eukaryotic enzyme. However, CuZn SODs adopting the monomeric configuration have recently been isolated from E. coli. Since the monomeric bacteriocuprein activity was determined to be comparable to that of the dimeric protein, this showed that the subunit interaction does not play a role in the protein’s activity. Hence, the human/ E. coli CuZn SOD chimeric protein (L-Loopy SOD), has been genetically engineered, in an attempt to produce a stable, active, monomeric human CuZn SOD, for therapeutic applications. The human wild-type CuZn SOD has also been mutated to express this dimeric protein (L-1 SOD) in E. coli cytoplasm.