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

A novel cytochrome P450, CYP4F8, was recently cloned from human seminal ves icles. CYP4F8 was expressed in yeast. Recombinant CYP4F8 oxygenated arachid onic acid to (18R)-hydroxyarachidonate, whereas prostaglandin (PG) D-2, PGE (1), PGE(2), PGF(2 alpha), and leukotriene B-4 appeared to be poor substrat es. Three stable PGH, analogues, 9,11-epoxymethano-PGH(2) (U-44069), 11,9-e poxymethano-PGH(2) (U-46619), and 9,11-diazo-18-deoxy-PGH(2) (U-51605) were rapidly metabolized by omega 2- and omega 3-hydroxylation, U-44069 was oxy genated with a V-max of similar to 260 pmol min(-1) pmol P450(-1) and a K-m of similar to 7 mu M. PGH(2) decomposes mainly to PGE(2) in buffer and to PGF(2 alpha) by reduction with SnCl2. CYP4F8 metabolized PGH(2) to 19-hydro xy-PGH(2), which decomposed to 19-hydrsxy-PGE(2) in buffer and could be red uced to 19-hydroxy-PGF(2 alpha) with SnCl2. 18-Hydroxy metabolites were als o formed (similar to 17%). PGH(1) was metabolized to 19- and 18-hydroxy-PGH (1) in the same way. Microsomes of human seminal vesicles oxygenated arachi donate, U-44069, U-46619, U-51605, and PGH(2), similar to CYP4F8, (19R)-Hyd roxy-PGE(1) and (19R)-hydroxy-PGE(2) are the main prostaglandins of human s eminal fluid. We propose that they are formed by CYP4F8-catalyzed omega 2-h ydroxylation of PGH, and PGH, in the seminal vesicles and isomerization to (19R)-hydroxy-PGE by PGE synthase. CYP4F8 is the first described hydroxylas e with specificity and catalytic competence for prostaglandin endoperoxides .