Lactoferrin-mediated formation of oxygen radicals by NADPH-cytochrome P-450 reductase system.
Superoxide generation in the NADPH oxidase reaction of NADPH-cytochrome P-450 reductase, demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline-1-oxide, increased on the addition of lactoferrin. The NADPH-lactoferrin reductase activity was assessed in terms of NADPH oxidation and oxygen consumption. From Lineweaver-Burk plots, the Km and Vmax for lactoferrin were estimated to be 13 microM and 0.5 S-1, respectively. The liberation of iron from lactoferrin was proven with the use of bathophenanthroline and by the demonstration of bleomycin-dependent DNA degradation; lactoferrin was reduced by the enzyme in the presence of NADPH. During the reaction, the ESR spectrum of the spin trap adduct changed from one characteristic of DMPO-OOH to that of DMPO-OH. The conversion was ascribed to the reaction of hydrogen peroxide with reduced lactoferrin.
Nakamura
M
M
Division of Biophysics, Hokkaido University.
D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D001761:Bleomycin / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism; D005609:Free Radicals; D066298:In Vitro Techniques; D007700:Kinetics; D007781:Lactoferrin / Q000378:metabolism*; D007782:Lactoglobulins / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D010101:Oxygen Consumption; D051381:Rats; D013056:Spectrophotometry, Ultraviolet; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D005609:Free Radicals; D007782:Lactoglobulins; D001761:Bleomycin; D013481:Superoxides; D002374:Catalase; D013482:Superoxide Dismutase; D009251:NADPH-Ferrihemoprotein Reductase; D007781:Lactoferrin