Formation of free radical metabolites in the reaction between soybean lipoxygenase and its inhibitors. An ESR study |
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Authors: | J Van der Zee T E Eling R P Mason |
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Institution: | Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709. |
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Abstract: | Recent studies showed that soybean lipoxygenase inhibitors like phenidone and nordihydroguaiaretic acid (NDGA) reduce the catalytically active ferric lipoxygenase to its inactive ferrous form. Addition of 13(S)-hydroperoxy-cis-9,trans-11-octadecadienoic acid (13-HPOD) regenerated the active ferric form. In this paper, it is shown that in such a system the inhibitors are oxidized to free-radical metabolites. Incubation of soybean lipoxygenase and linoleic acid with p-aminophenol, catechol, hydroquinone, NDGA, or phenidone resulted in the formation of the one-electron oxidation products of these compounds. Free-radical formation depended upon the presence of the lipoxygenase and 13-HPOD. The free radicals were detected by ESR spectroscopy, and their structure was confirmed by analysis of the spectra, using a computer correlation technique. These data support the proposed mechanism for the inhibition of lipoxygenase by phenolic antioxidants. |
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