title: Oxidation of prostaglandin H(2) and prostaglandin H(2) analogues by human cytochromes P450: analysis of omega-side chain hydroxy metabolites and four steroisomers of 5-hydroxyprostaglandin I(1) by mass spectrometry.
abstract: The objective was to examine the NADPH-dependent oxygenation of prostaglandin H(2) (PGH(2)) and three PGH(2) analogues, 9,11-diazo-15-deoxy-PGH(2) (U51605), 9,11-epoxymethano-PGH(2) (U44069), and 11,9-epoxymethano-PGH(2) (U46619), by cytochromes P450, and to characterize the metabolites by mass spectrometry. CYP2C19, CYP4A11, CYP4F8, and liver and renal cortical microsomes oxidized the omega-side chain of U44069, U46619, and U51605, whereas only CYP4F8 oxidized the omega-side chain of PGH(2). PGH(2) was transformed to four stereoisomers of 5-hydroxy-PGI(1) by recombinant cytochromes P450. CYP4F8 formed the 5-hydroxy-PGI(1) isomers in small amounts compared to the 19-hydroxy metabolites of PGH(2). Isomers of 5-hydroxy-PGI(1) and 6-keto-PGF(1 alpha) were detectable when PGH(2) decomposed in the presence of hemin, hemoglobin, or heat-inactivated microsomes. 5-Hydroxy-PGI(1) is likely formed from PGH(2) in a pseudo-enzymatic reaction involving homolytic scission of the endoperoxide and formation of an ether between C-9 and C-6 and a carbon-centered radical at C-5, which reacts with molecular oxygen. CYP4F8 catalyzes 19-hydroxylation of PGH(2), but the absolute configuration of the 19-hydroxy group is unknown, whereas human seminal fluid contains (19R)-hydroxy-PGE(2). CYP4F8 was found to metabolize U51605 to 90% of the (19R)-hydroxy metabolite, providing further evidence in favor of a role of CYP4F8 in biosynthesis of (19R)-hydroxy PGE in human seminal vesicles. We conclude that omega-side chain hydroxylation of PGH(2) analogues may be catalyzed by many different cytochromes P450, but only CYP4F8 oxidizes the omega-side chain of PGH(2) efficiently.
authors.affiliation: Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala Biomedical Centre, Uppsala University, SE-751 24 Uppsala, Sweden. Ernst.Oliw@farmbio.uu.se
authors.forename: E H
authors.initials: EH
authors.lastname: Oliw
authors.forename: K
authors.initials: K
authors.lastname: Stark
authors.forename: J
authors.initials: J
authors.lastname: Bylund
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002853:Chromatography, Liquid; D065731:Cytochrome P-450 CYP2C19; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D011464:Epoprostenol / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006900:Hydroxylation; D007672:Kidney Cortex / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D013058:Mass Spectrometry; D008861:Microsomes / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008968:Molecular Conformation; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D011448:Prostaglandin Antagonists / Q000378:metabolism; D044262:Prostaglandin H2; D011463:Prostaglandins H / Q000737:chemistry / Q000378:metabolism*; D051381:Rats
chemical_list: C040763:5-hydroxyprostaglandin I; D011448:Prostaglandin Antagonists; D011463:Prostaglandins H; D044262:Prostaglandin H2; D009249:NADP; C015014:azo analog I; D003577:Cytochrome P-450 Enzyme System; D011464:Epoprostenol; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; C120451:CYP4F8 protein, human; D065731:Cytochrome P-450 CYP2C19; D042926:Cytochrome P-450 CYP4A