Comparison of substrate specificities of the human placental NAD- and NADP-linked 15-hydroxyprostaglandin dehydrogenases

A study of the relative activity of the purified placental NAD- and NADP-linked 15-hydroxyprostaglandin dehydrogenases with various prostaglandins and thromboxane B₂(TxB₂) suggests that most, if not all, oxidation in the placenta of the 15-hydroxyl group of prostaglandins of the A, E, and F series as well as PGI₂ (prostacyclin) and 6-keto PGF_1α is catalyzed by the NAD-linked enzyme. Prostaglandin B₁ is an excellent substrate for the NADP-linked enzyme. Despite the conformational similarities between PGB₁ and PGI₂, the latter molecule is a poor substrate for the NADP-linked enzyme. Thromboxane B₂ is not oxidized by the NAD-linked enzyme and is oxidized slowly by the NADP-linked enzyme.