The peroxidase activity of bleomycin-Fe3+ is associated with damage to biological components

In this study, bleomycin-Fe3+ steadily oxidized tetramethylbenzidine (TMB) in the presence of peroxides. However, the ability of bleomycin-Fe3+ to function as a peroxidase was extremely low compared with that of other peroxidases. A characteristic property of bleomycin-Fe3+ different from that observed for other peroxidases is its ability to oxidize TMB at the similar rate at both a pH 5 and 8 in the presence of lipid hydroperoxide (LOOH). In the present experiments, hydroxyl radicals (HO center dot) were generated only when bleomycin-Fe3+ was incubated with H2O2 at a pH of 5. No generation of HO center dot was observed during the incubation of bleomycin-Fe3+ with LOOH. Meanwhile, bleomycin-Fe3+ induced the formation of LOOH from linoleic acid and alcohol dehydrogenase was inactivated by bleomycin-Fe3+ with peroxides. Thiobarbituric acid reactive substances were formed from DNA by bleomycin-Fe3+ with H2O2, and strand breaks were caused by bleomycin-Fe3+ with LOOH. The oxidative substrates for bleomycin-Fe3+ blocked the damage to biological components induced by bleomycin-Fe3+. These results suggest that compound I-like species contribute to the process of damage to biological components induced by bleomycin-Fe3+.