Transformation of an arachidonic acid hydroperoxide into epoxyhydroxy and trihydroxy fatty acids by liver microsomal cytochrome P-450.
In the absence of NADPH, the addition of an arachidonic acid hydroperoxide, 15-hydroperoxyeicosa-5,8,11,13-tetraenoic acid, to liver microsomes, prepared from phenobarbital-treated rats, resulted in the formation of two major metabolites and several minor products, some of which have been purified by reverse-phase high-performance liquid chromatography. We propose the structures of the two major products to be 13-hydroxy-14,15-epoxyeicosa-5,8,11-trienoic acid and 11,14,15-trihydroxyeicosa-5,8,12-trienoic acid based on spectral characteristics and mass spectral analysis of derivatives of the compounds. A potential heterolytic cleavage product, 15-hydroxyeicosa-5,8,11,13-tetraenoic acid, was not a product of the reaction. Ferric cytochrome P-450 catalyzed the formation of these products as shown by the inability of boiled microsomes to support the reaction, the inhibition of epoxyhydroxy and trihydroxy fatty acid formation by imidazole derivatives which bind tightly to the ferric heme iron of cytochrome P-450, and the inability of carbon monoxide (which binds to ferrous P-450) and free iron chelators (EDTA and diethylenetriaminepentaacetic acid) to inhibit product formation. These results show that liver microsomal cytochrome P-450, in addition to its role in the NADPH-dependent metabolism of arachidonic acid, can utilize a hydroperoxide to produce an interesting series of potentially important arachidonic acid metabolites.
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D006358:Hot Temperature; D007093:Imidazoles / Q000494:pharmacology; D015289:Leukotrienes; D008054:Lipid Peroxides / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013053:Spectrophotometry
D001095:Arachidonic Acids; D065607:Cytochrome P-450 Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D007093:Imidazoles; D015289:Leukotrienes; D008054:Lipid Peroxides; C025086:15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; C051282:13-hydroxy-14,15-epoxyeicosa-5,8,11-trienoic acid; C051283:11,14,15-trihydroxyeicosa-5,8,12-trienoic acid; D003577:Cytochrome P-450 Enzyme System; D015126:8,11,14-Eicosatrienoic Acid