Superoxide-Superoxide Oxidoreductase Activity of the Captopril-Copper Complex

Background rpose of this study was to determine whether the interaction of captopril, an angiotensin-converting enzyme inhibitor, with copper could modify the superoxide dismutase activity of this metal. Results may help to explain the interaction of captopril with reactive oxygen species in the stunned myocardium where substantial mobilization of copper and iron in the coronary flow following ischemia has been reported. s ay that generates superoxide anion radicals without the intervention of metal ions was utilized. In addition, direct EPR analysis was applied to assess the redox state of copper during reactions. s ril-copper complex inhibited the superoxide-mediated reduction of nitroblue tetrazolium. In addition, captopril-copper complex was able to suppress formazan production by potassium superoxide. Direct EPR analysis showed that copper was reduced to the cuprous state by captopril and remained in this state in the course of the reaction. Captopril was also stable during the dismutation reaction. sions clude that cuprous-captopril complex is a catalytic species with properties different from those of Cu2+ alone. A model in which sulfur acts as electron acceptor/donor in place of the metal is proposed and a mechanism of action for this complex is discussed.