Oxygenation of 5,8,11-Eicosatrienoic Acid by Prostaglandin Endoperoxide Synthase and by Cytochrome P450 Monooxygenase: Structure and Mechanism of Formation of Major Metabolites
| Autor: | Mats Hamberg, Lena Hörnsten, Howard Sprecher, Ernst H. Oliw |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Male
Stereochemistry Metabolite Biophysics Alcohol Biochemistry Gas Chromatography-Mass Spectrometry Catalysis chemistry.chemical_compound 8 11 14-Eicosatrienoic Acid Cytochrome P-450 Enzyme System Microsomes Animals Molecular Biology Chromatography High Pressure Liquid chemistry.chemical_classification Sheep biology Diastereomer Cytochrome P450 Monooxygenase Oxygen Enzyme chemistry Prostaglandin-Endoperoxide Synthases Oxygenases biology.protein Microsome Eicosanoids |
| Zdroj: | Archives of Biochemistry and Biophysics. 305:288-297 |
| ISSN: | 0003-9861 |
| DOI: | 10.1006/abbi.1993.1425 |
| Popis: | Incubation of 5,8,11-[1- 14 C]eicosatrienoic acid with prostaglandin endoperoxide synthase of ram vesicular gland microsomes led to formation of a number of polar metabolites. Four major compounds were characterized by chemical and physical methods and found to be: (13 R )-hydroxy-5,8,11-eicosatrienoic acid, (11 R )-hydroxy-5,8,12-eicosatrienoic acid, 8,9,11-trihydroxy-5,12-eicosadienoic acid (two diastereoisomers), and 8,9-epoxy-11-hydroxy-5,12-eicosadienoic acid. On the basis of previous studies on the mechanism of prostaglandin biosynthesis it seemed likely that the initial step of conversion of 5,8,11-eicosatrienoic acid consisted of removal of the pro-S hydrogen from C-13. The resulting carbon-centered radical was apparently attacked by dioxygen at C-13 to provide a (13 R )-(hydro)peroxy derivative, which served as the precursor of (13 R )-hydroxyeicosatrienoic acid. Alternatively, attack by dioxygen occurred at C-11 to produce an (11 R )-peroxy radical. This intermediate was further converted to (11 R )-hydroxyeicosatrienoic acid by reduction, into two 8,9,11-trihydroxy-5,12-eicosadienoic acids by successive cyclization, oxygenation, and reduction, and into the epoxy-hydroxy acid by cyclization and intramolecular epoxidation. The relative abundance of (13 R )-hydroxy-5,8,11-eicosatrienoic acid, (11 R )-hydroxy-5,8,12-eicosatrienoic acid, and the epoxy alcohol plus the two 8,9,11-triols was 51, 9, and 40%, respectively. The oxygenation at C-13 and C-11 of 5,8,11-eicosatrienoic acid was inhibited by 90% in the presence of diclofenac, an inhibitor of prostaglandin endoperoxide synthase. The two diastereomeric 8,9,11-trihydroxy acids and the epoxy-hydroxy acid are novel oxylipins and their formation provides independent chemical evidence for the existence of an 11-peroxy radical intermediate in prostaglandin endoperoxide synthase catalysis. Oxygenation of 5,8,11-eicosatrienoic acid by cytochrome P450 from liver microsomes of cynomolgus monkeys and phenobarbital-treated rats was also investigated. The metabolites formed included 19- and 20-hy-droxyeicosatrienoic acid, 8,9- and 11,12-dihydroxyeicosadienoic acids (formed by enzymatic hydrolysis of the corresponding epoxides), and (12 R )-hydroxy-5,8,10-hydroxyeicosatrienoic acid. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|