[Generation of superoxide anion by the reaction of bleomycin-Cu (II) with cysteine].

: We examined if superoxide anions would be produced when bleomycin-Cu (II) were incubated with cysteine under an aerobic condition. Strong reductions of cytochrome c and nitroblue tetrazolium chloride were observed when 0.065 mM bleomycin-Cu (II) and 0.1 mM cysteine were incubated. Neocuproine, which binds specifically with Cu (I), inhibited the reduction of both agents, while superoxide dismutase inhibited only the reduction of nitroblue tetrazolium chloride. These results suggest that cytochrome c is directly reduced by the cuprous ion released from bleomycin-Cu (II) in a reducing reaction with cysteine and nitroblue tetrazolium chloride is reduced by the superoxide anion formed in the reaction of the cuprous ion with oxygen.