Stimulation of prolyl hydroxylase activity by bleomycin

The activity of purified prolyl hydroxylase (proline, 2-oxoglutarate dioxygenase, EC 1. 14. 11. 2) was enhanced 3 approximately 8-fold at a low concentration of ferrous ion (1 X 10(-5 M) by addition of bleomycin, a glycopeptide antibiotic with antineoplastic activity and a side effect of producing pulmonary fibrosis. The maximum stimulation was attained at a concentration of 15 microgram/ml bleomycin (about 1 X 10(-5) M), which was approximately equimolar with the ferrous ion, one of the cofactors of this enzyme. Addition of bleomycin to the assay mixture resulted in a change of the optimal concentration of ferrous ion from 2 X 10(-3) M to 1 X 10(-5) M. Changing the order of addition of ferrous ion, enzyme and bleomycin in assay medium before incubation at 37 degrees C, the stimulatory activity was varied. Blemycin A2Cu++(Cu++-chelated bleomycin), which scarcely complexed with Fe++, had no enhancing effects on the enzymatic activity. We discuss the possible reasons as to why the activity of prolyl hydroxylase was enhanced by addition of bleomycin in the assay mixture.