Hydroperoxidative Oxidation of Diethylstilbestrol by Lipoxygenase

The oxidation of diethylstilbestrol (DES), a synthetic carcinogenic estrogen, by the hydroperoxidase activity of lipoxygenase was studied. Lipoxygenase catalyzes the oxidation of DES to its corresponding DES quinone to yield free radical species intermediates (DES semiquinone and DES quinone), which are associated with the adverse effects of this synthetic estrogen. The reaction was dependent on enzyme, DES, and hydrogen peroxide concentrations. Due to the low degree of water solubility of DES, the enzyme works in a range of DES concentrations belowKm. The enzyme presents a high affinity for hydrogen peroxide (5.7 μM), and produces substrate inhibition (Ksi= 2.5 mM). This study is the first demonstration that this reaction, which is known to be catalyzed by a variety of enzymes, including peroxidases, is also catalyzed by lipoxygenase.