Metabolism of prostacyclin. Oxidation by rhesus monkey lung 15-hydroxyl prostaglandin dehydrogenase.

Partially purified rhesus monkey lung 15-hydroxyl prostaglandin dehydrogenase (15-OH PGDH) catalyzed the NAD-dependent oxidation of prostacyclin (PGI₂) and 6-keto-PGF_1a to 6,15-diketo-PGF_1a. The product was identified by gas chromatography-mass spectroscopy. Prostacyclin was oxidized four to six times faster than 6-keto-PGF_1a under identical reaction conditions, suggesting that the metabolism of prostacyclin probably proceeds through a bicyclic 15-keto intermediate before chemically decomposing to the final stable product, 6,15-diketo-PGF_1a. Prostacyclin has a good affinity for the 15-OH PGDH enzyme. A Lineweaver-Burke plot gave an apparent K_m value of 7.4 μm, which compares very favorably with the K_m values for PGE₁ and PGE₂.