Oxygen transfer from bleomycin-metal complexes

Both Fe(III) and Cu(II) complexes of bleomycin (BLM), but not N-acetyl BLM · Fe(III), mediated the transfer of oxygen from iodosobenzene to organic substrates. In analogy with results obtained using certain cytochrome P-450 analogs, cis-stilbene was converted cleanly to the respective oxide, while no more than traces of trans-stilbene oxide were formed from trans-stilbene under identical conditions. The possible relevance of these observations to the degradation of DNA by bleomycin was also studied. In both the presence and absence of O₂, BLM · Cu(II) · C₆H₅IO effected DNA degradation, as judged by the release of [³H]thymine from radiolabeled Escherichia coli DNA. These findings provide a valuable new assay system for the study of bleomycin analogs and suggest the possibility that bleomycin may function as an 'oxygen transferase' in its degradation of DNA in situ.