In enzymology, a prostaglandin-E<sub>2</sub> 9-reductase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are prostaglandin E<sub>2</sub> and oxidised nicotinamide adenine dinucleotide phosphate (NADP<sup>+</sup>). Its products are prostaglandin F<sub>2ñ</sub>, reduced NADPH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is (5Z,13E)-(15S)-9alpha,11alpha,15-trihydroxyprosta-5,13-dienoate:NADP<sup>+</sup> 9-oxidoreductase. Other names in common use include PGE<sub>2</sub>-9-OR, reductase, 15-hydroxy-9-oxoprostaglandin, 9-keto-prostaglandin E<sub>2</sub> reductase, 9-ketoprostaglandin reductase, PGE-9-ketoreductase, PGE<sub>2</sub> 9-oxoreductase, PGE<sub>2</sub> reductase-9-ketoreductase, prostaglandin 9-ketoreductase, prostaglandin E 9-ketoreductase, and prostaglandin E<sub>2</sub> reductase-9-oxoreductase. This enzyme participates in arachidonic acid metabolism.
As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .