Early steps in prostaglandin metabolism in the human placenta.
The activities of the enzymes catalyzing in the early steps in prostaglandin metabolism (the nicotinamide adenine dinucleotide [NAD]-linked 15-hydroxyprostaglandin dehydrogenase, the nicotinamide adenine dinucleotide phosphate [NADP]-linked 15-hydroxyprostaglandin dehydrogenase, and the 15-ketoprostaglandin delta 13 reductase) were measured in homogenates of term placenta. The NAD-linked enzyme possesses the highest activity of the three. The NADP-linked enzyme has much lower activity and probably acts physiologically as a 9-ketosprostaglandin reductase rather than as a 15-hydroxyprostaglandin dehydrogenase. Placental homogenates contain a low-molecular-weight, heat-stable inhibitor of the NADP-linked enzyme. The reaction catalyzed by the 15-ketoprostaglandin delta 13 reductase is the rate-limiting step. Analysis of the activity of these enzymes has shown that there is no significant relationship between them; furthermore, whether the placentas are from spontaneous single or twin deliveries, induced deliveries, or cesarean sections (in labor or not in labor) does not have a significant effect on the activity of the NAD- or NADP-linked dehydrogenases.
D011452:15-Oxoprostaglandin 13-Reductase / Q000378:metabolism; D036861:Delivery, Obstetric / Q000379:methods; D004791:Enzyme Inhibitors / Q000378:metabolism; D005260:Female; D006801:Humans; D006911:Hydroxyprostaglandin Dehydrogenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011453:Prostaglandins / Q000378:metabolism*; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D011453:Prostaglandins; D006911:Hydroxyprostaglandin Dehydrogenases; D011452:15-Oxoprostaglandin 13-Reductase