The redox state of activated bleomycin

Activated bleomycin appears to have two more oxidizing equivalents than the Fe(III)·bleomycin to which it spontaneously decays. Activated bleomycin reacts with NADH and thio-NADH, two-electron reductants, and with KI, a one-electron reductant, to yield Fe(III)·bleomycin. The observed stoichiometries were 0.85 ± 0.07 eq of thio-NADH oxidized or 1.5 ± 0.25 eq of KI oxidized per mole of activated bleomycin. None of these reactions requires the presence of a redox mediator, as does the reduction of Fe(III)·bleomycin by NADH or thio-NADH. The oxidations of both pyridine nucleotide coenzymes and of KI are inhibited by DNA, the usual bleomycin target.