J. Bylund, M. Hidestrand, M. Ingelman-Sundberg
Jul 21, 2000
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4
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76
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Journal
The Journal of Biological Chemistry
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, PGF2α, 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 aV max of ∼260 pmol min− 1 pmol P450− 1 and a K m of ∼7 μm. PGH2decomposes mainly to PGE2 in buffer and to PGF2α 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-PGF2α with SnCl2. 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.