Polymers of Cu/Zn superoxide dismutase produced by cross-linking with glutaraldehyde

Soluble polymers of bovine Cu/Zn superoxide dismutase (EC 1.15.1.1) have been prepared using the homobifunctional cross-linking reagent, glutaraldehyde. A form of the enzyme, a tetramer, with a molecular weight of 64,000 has been purified by gel filtration. The functional properties of the tetramer have been investigated. Reconstitution with copper and zinc was required for full activity. After metal reconstitution, the specific activity of the tetramer was shown to be close to 90% that of the native dimeric enzyme. The serum half-life of the tetramer in rats was found to be increased by a factor of six when compared with native superoxide dismutase. The tissue distribution of the two forms was also found to be different with the tetramer accumulating predominantly in the liver.