prostaglandin-I synthase activity https://github.com/geneontology/go-ontology/issues/30193 (5Z,13E)-(15S)-9alpha,11alpha-epidioxy-15-hydroxyprosta-5,13-dienoate 6-isomerase activity prostacycline synthetase activity KEGG_REACTION:R02267 molecular_function Reactome:R-HSA-76496 PGI(2) synthase activity PGI2 synthetase activity GO:0008116 PGI2 synthase activity RHEA:23580 PGI(2) synthetase activity Catalysis of the reaction: prostaglandin H(2) = prostaglandin I(2). cytochrome P450 CYP8A1 prostacyclin synthase activity MetaCyc:PROSTAGLANDIN-I-SYNTHASE-RXN EC:5.3.99.4 prostagladin I2 synthetase activity intramolecular oxidoreductase activity