Human 5-lipoxygenase contains an essential iron.

The iron content of human 5-lipoxygenase has been determined by a colorimetric assay using the chromogenic ligand FerroZine. The highly active enzyme was obtained from a baculovirus expression system and purified using an ATP-agarose chromatography column (Denis, D., Falgueyret, J.-P., Riendeau, D., and Abramovitz, M. (1991) J. Biol. Chem. 266, 5072-5079). A linear correlation was observed between the enzyme's specific activity and iron content in six different preparations. Enzyme with the highest specific activity (24 mumol of 5-hydroperoxyeicosatetraenoic acid/mg of protein) contained 1.1 mol of iron/mol of enzyme, whereas inactive enzyme contained no detectable iron. The iron is tightly bound to the enzyme and could only be released after inactivation of the enzyme by exposure to oxygen.