Porcine leukocyte 5‐ and 12‐lipoxygenases are iron enzymes

Abstract

5‐ and 12‐lipoxygenases isolated from porcine leukocytes were investigated by electron paramagnetic resonance at X‐band and atomic absorption spectroscopy. For comparison potato 5‐lipoxygenase was studied under identical experimental conditions. All three lipoxygenases contained between 0.7 and 0.9 Fe atoms/enzyme molecule. As isolated, both mammalian enzymes exhibited a characteristic EPR signal at low magnetic field with a maximum at g =5.20 indicative of a high‐spin ferric iron center. The signal was not affected by the oxidants 12‐hydroperoxyeicosatetraenoic acid or arachidonic acid, nor was it affected by the reductant nordihydroguaiaretic acid. In the case of the potato enzyme an intense EPR signal with resonances at g =7.50, 6.39 and 5.84 was only observed after addition of an oxidant, such as 9‐hydroperoxyoctadecadienoic acid.