Biosynthesis of 18(RD)-hydroxyeicosatetraenoic acid from arachidonic acid by microsomes of monkey seminal vesicles. Some properties of a novel fatty acid omega 3-hydroxylase and omega 3-epoxygenase.
Microsomes of seminal vesicles of the cynomolgus monkey were incubated with [14C]5,8,11,14-eicosatetraenoic (arachidonic) acid and NADPH for 40 min at 37 degrees C and the products were characterized. Prostaglandins F2 alpha and E2 were the two main metabolites (approximately 52% of radioactivity), while 18(R)-hydroxy-cis-5,8,11,14-eicosatetraenoic acid (18(R)-HETE) was identified as the main, less polar product (approximately 13%). Significant biosynthesis of the 19-hydroxy or 20-hydroxy metabolites of arachidonic acid could not be detected. The formation of 18(R)-HETE was further investigated in the presence of a prostaglandin synthesis inhibitor, diclofenac sodium. The omega 3-hydroxylation was only partly supported by substituting NADH for NADPH. The hydroxyl oxygen of 18(R)-HETE was derived from the atmosphere and the omega 3-hydroxylation was inhibited by proadifen and partly inhibited by carbon monoxide. These findings suggest that 18(R)-HETE is formed by a cytochrome P-450 (P-450 omega 3). Linoleic acid and 8,11,14-eicosatetraenoic acid were also substrates of the enzyme, but stearic acid was not metabolized. 5,8,11,14,17-Eicosatetraenoic acid was oxygenated under these conditions mainly to 17,18-dihydroxy-5,8,11,14-eicosatetraenoic acid, presumably formed from 17(18)-epoxy-5,8,11,14-eicosatetraenoic acid by hydrolysis. The seminal microsomes thus seem to possess both omega 3-hydroxylase and omega 3-epoxygenase activity. These seminal vesicles also contain prostaglandin E 19-hydroxylase (Oliw, E.H., Kinn, A.-C., and Kvist, U. (1988) J. Biol. Chem. 263, 7222-7227). The presence of arachidonate omega 3-hydroxylase and prostaglandin E 19-hydroxylase was assessed in microsomes of adult and juvenile monkey livers. Arachidonic acid was metabolized extensively to diols (via epoxides), but 18-HETE could not be detected. In contrast, prostaglandin E1 was slowly hydroxylated mainly to 19-hydroxyprostaglandin E1 by both adult male and female juvenile hepatic microsomes. The results indicate that P-450 omega 3 of seminal vesicles might be a tissue-specific enzyme.
Oliw
E H
EH
Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D000090762:Cytochrome P-450 CYP2J2; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006893:Hydroxyeicosatetraenoic Acids; D008252:Macaca fascicularis; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D011453:Prostaglandins / Q000096:biosynthesis; D012669:Seminal Vesicles / Q000201:enzymology*
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D011453:Prostaglandins; C061444:18-hydroxy-5,8,11,14-eicosatetraenoic acid; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2; D042926:Cytochrome P-450 CYP4A