The influence of copper ion on enzyme activity of hog liver copper zinc superoxide dismutase (CuZnSOD) was monitored by using the pyrogallol autoxidation inhibition assay. The direct interaction of copper ion with CuZnSOD was studied by fluorescence spectroscopy, and a type of 1∶1 stable complex has been generated, which was certified by the quenching experiment of intrinsic fluorescence. The process of the generated complex shown by dynamic analysis of fluorescence quenching, consisted of two steps, in which the first step was a quick association process of double molecules to generate a loose complex, and the second step was a slow process of single molecule, where the loose complex was isomerized into the compact complex. The change of enzyme conformation was due to the binding of Cu^2＋to SOD, which was confirmed by FTIR and CD spectra.

Key words: CuZnSOD, fluorescence spectroscopy, copper ion, hog liver