Prostacyclin synthase (also known as prostaglandin I2 (prostacyclin) synthase (PTGIS) or CYP8A1) () catalyses the isomerization of prostaglandin H2 to prostacyclin. It plays an important role for prostanoid biosynthesis in humans. Although it shows homology with cytochrome P450, it does not require molecular oxygen. Instead it uses its heme cofactor to catalyse the isomerization of prostaglandin H2 to prostacyclin [, ].
