Stereoselective epoxidation of arachidonic acid by cytochrome P-450s 2CAA and 2C2.
In the present study, we determined the stereoselective epoxidation of arachidonic acid by cytochrome P-450 (P-450) 2CAA and P-450 2C2, two arachidonic acid epoxygenases found in rabbit renal cortex, by chiral normal-phase high-performance liquid chromatography (HPLC)-analysis. Purified P-450 2CAA reconstituted with P-450 oxidoreductase, lipid and cytochrome b5 or microsomes isolated from COS-1 cells expressing P-450 2C2 were incubated in the presence of [1-14C]arachidonic acid. The epoxide metabolites 14,15- and 11,12-epoxyeicosatrienoic acids (EETs) were purified by reverse-phase HPLC and derivatized to methyl (14,15-EET) and pentafluorobenzyl (11,12-EET) esters. Enantiomers of 14,15-EET-methyl ester and 11,12-EET-pentafluorobenzyl ester were resolved on Chiralcel OB and OD columns, respectively, with a mobile phase of 0.15% 2-propanol in n-hexane. P-450 2CAA and P-450 2C2 produce 11,12- and 14,15-EETs in distinct ratios but are equally stereoselective at the 11,12-position. P-450 2CAA produced 11(S), 12(R)-EET with 63% stereoselectivity, and P-450 2C2 produced the same enantiomer with 61% stereoselectivity. Both enzymes are also stereoselective at the 14,15- position, preferentially producing the 14(R), 15(S)-EET. P-450 2CAA produces this enantiomer with 72% selectivity, and P-450 2C2 produces it with 62% selectivity. The results of this study indicate that P-450 2CAA and P-450 2C2 are not only regioselective but also exhibit a high degree of stereoselectivity.
Daikh
B E
BE
Department of Pharmacology, Oregon Health Sciences University, Portland.
Laethem
R M
RM
Koop
D R
DR
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D000090762:Cytochrome P-450 CYP2J2; D003577:Cytochrome P-450 Enzyme System / Q000494:pharmacology*; D004852:Epoxy Compounds / Q000378:metabolism*; D010105:Oxygenases / Q000494:pharmacology*; D011817:Rabbits; D013237:Stereoisomerism
D004852:Epoxy Compounds; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2