Observations on the substrate specificity of prostaglandin hydroxylases of monkey seminal vesicles and sheep vesicular glands.

Prostaglandin (PG) 19-hydroxylase of monkey seminal vesicles metabolizes PGE1 and PGE2 to their 19-hydroxy metabolites, while PGE2 20-hydroxylase of ram vesicular glands metabolizes PGE2 to 20-hydroxy-PGE2. The purpose of the present study was determine whether PGF2 alpha is a substrate of these enzymes. Deuterated 20-hydroxy-PGF2 alpha was employed as an internal standard to study the hydroxylation of PGF2 alpha (0.2 mM) by microsomes of monkey (Macaca fascicularis) seminal vesicles in the presence of NADPH, and the biosynthesis was compared with the hydroxylation of PGE2 under identical conditions. 19-Hydroxy-PGF2 alpha was formed at a rate of 3.5% of the formation of 19-hydroxy-PGE2. Microsomes of ram vesicular glands also hydroxylated PGE2 more efficiently than PGF2 alpha, which was converted to both 20-hydroxy-PGF2 alpha and 19-hydroxy-PGF2 alpha at a combined rate of 5% of the biosynthesis of 20-hydroxy-PGE2 under the same conditions. 20-Hydroxy-PGF2 alpha was demonstrated in ram semen, but the concentration was low (0.1 microM) in comparison with 20-hydroxy-PGE2 (24 microM). The two genital PG hydroxylases thus metabolize PGF2 alpha much less efficiently than PGE2. This finding may suggest that 19-hydroxy- and 20-hydroxy-PGF2 alpha in seminal fluids also could be formed by other mechanisms, e.g., from 19-hydroxy- and 20-hydroxy-PGE2 by the PGE 9-keto reductase enzyme.