OBSERVATIONS ON THE DIRECT ELECTROCHEMISTRY OF BOVINE COPPER-ZINC SUPEROXIDE-DISMUTASE

The cyclic voltammetric behavior of holo-superoxide dismutase (SOD) at pH 4.0 consists of an anodic peak at +0.270 V/SCE with no evidence of a cathodic feature on the forward (reduction) scan. Chronocoulometric data suggest that the reduced enzyme is strongly adsorbed in a close-packed arrangement. Background-subtracted differential pulse voltammograms yield poorly defined cathodic and anodic peaks at pH 5.0-7.0. Chemically reduced holo-SOD solutions exhibit markedly improved differential pulse voltammetric characteristics (especially the anodic), thus suggesting a conformational change occurring, possibly at the active site, consequent to electrochemical/chemical reduction that, in turn, enhances accessibility of the electrode to the active site.