GO:0050221

Catalysis of the reaction: (5Z,13E)-(15S)-9-alpha,11-alpha,15-trihydroxyprosta-5,13-dienoate + NADP+ = (5Z,13E)-(15S)-11-alpha,15-dihydroxy-9-oxoprosta-5,13-dienoate + NADPH. [EC:1.1.1.189, MetaCyc:PROSTAGLANDIN-E2-9-REDUCTASE-RXN]