Interaction of p-phenylenediamine with the iron-bleomycin complex

The iron-bleomycin complex has been shown to catalyze the oxidation of p-phenylenediamine to a stable, purple coloured oxidation product, characterized by an absorption maximum around 520 nm. Molecular oxygen is used for reoxidizing Fe(II)-bleomycin after reduction by p-phenylenediamine. An apparent Michaelis constant of 5.2 mM and a catalytic constant of 17.2 min-1 were obtained from kinetic studies. ATP, ADP and orthophosphate inhibited the catalytic oxidation of p-phenylenediamine, while AMP was without effect. It is proposed that p-phenylenediamine may be used as 'substrate' in kinetic studies involving the 'oxidase' activity of iron-bleomycin.