Stimulatory effect of ascorbate on iron transfer from bleomycin to apotransferrin.
The chemotherapeutic agent, bleomycin, forms a 1:1 complex with both Fe(III) and Fe(II). The rate of ferric ion transfer from bleomycin to apotransferrin is rather slow. However, when ascorbate was added to Fe(III)-bleomycin prior to exposure to apotransferrin, the transfer rate was markedly increased. Ascorbate readily reduces Fe(III)-bleomycin to Fe(II)-bleomycin. A second order rate constant of 2.4 mM-1 min-1 was estimated for this reaction. Fe(II)-bleomycin immediately combines with O2, generating the so-called 'activated bleomycin' complex. The data suggest that a reduced form of iron-bleomycin more readily donates its iron ion to apotransferrin. Reoxidation of ferrous ions, and Fe(III)-transferrin formation occur rapidly.
Løvstad
R A
RA
Department of Medical Biochemistry, University of Oslo, Norway.
D000975:Antioxidants / Q000494:pharmacology*; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism*; D001205:Ascorbic Acid / Q000494:pharmacology*; D001761:Bleomycin / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D014168:Transferrin / Q000737:chemistry* / Q000378:metabolism*
D000975:Antioxidants; D001059:Apoproteins; D014168:Transferrin; C028284:apotransferrin; D001761:Bleomycin; D007501:Iron; D001205:Ascorbic Acid