Identification of CYP4F8 in human seminal vesicles as a prominent 19-Hydroxylase of prostaglandin endoperoxides

Abstract

A novel cytochrome P450, CYP4F8, was recently cloned from human seminal vesicles. CYP4F8 was expressed in yeast. Recombinant CYP4F8 oxygenated arachidonic acid to (18R)-hydroxyarachidonate, whereas prostaglandin (PG) D2, PGE1, PGE2, PGF2(}(A), and leukotriene B4 appeared to be poor substrates. Three stable PGH2 analogues, 9,11-epoxymethano-PGH2 (U-44069), 11,9-epoxymethano-PGH2 (U-46619), and 9,11-diazo-15-deoxy-PGH2 (U-51605) were rapidly metabolized by ω2- and ω3-hydroxylation. U-44069 was oxygenated with a V(max) of ~260 pmol min-1 pmol P450-1 and a K(m) of ~7μM. PGH2 decomposes mainly to PGE2 in buffer and to PGF2(}(a) by reduction with SnCl2. CYP4F8 metabolized PGH2 to 19-hydroxy-PGH2, which decomposed to 19-hydroxy-PGE2 in buffer and could be reduced to 19-hydroxy-PGF2(}(a) with SnC12. 18-Hydroxy metabolites were also formed (~17%). PGH1 was metabolized to 19-and 18-hydroxy-PGH1 in the same way. Microsomes of human seminal vesicles oxygenated arachidonate, U-44069, U-46619, U-51605, and PGH2, similar to CYP4F8. (19R)-Hydroxy-PGE1 and (19R)-hydroxy-PGE2 are the main prostaglandins of human seminal fluid. We propose that they are formed by CYP4F8-catalyzed ω2-hydroxylation of PGH1 and PGH2 in the seminal vesicles and isomerization to (19R)-hydroxy-PGE by PGE synthase. CYP4F8 is the first described hydroxylase with specificity and catalytic competence for prostaglandin endoperoxides.