Bleomycin Assay for Catalytic Iron Salts in Body Fluids

Formation of the highly reactive hydroxyl radical from hydrogen peroxide in biological systems requires the presence of traces of transition metal ions. Attention has primarily been paid to iron salts as catalysts, ^{1 - 4} but copper salts are also effective. ^{5 , 6} Many biochemical reagents, especially phosphate buffers and phosphate esters such as ADP, are contaminated with iron salts in amounts sufficient for hydroxyl radical formation to occur even without iron salt addition. ^{7 , 8} By contrast, iron bound to proteins such as hemoglobin, myoglobin, catalase, peroxidase, and superoxide dismutase (Fe SOD) is ineffective in catalyzing hydroxyl radical formation. There is some debate as to whether iron bound to transferrin ^{2 , 10 , 11} or lactoferrin ^{12 - 15} can catalyze this reaction, but if it can, then the effect is at best weak and is only seen when the proteins are fully iron-loaded (2 mol Fe (III) per mole of protein), a situation not often encountered in vivo. ^{11 , 14 , 15}