Prostaglandin-I synthase () also known as prostaglandin I2 (prostacyclin) synthase (PTGIS) or CYP8A1 is an enzyme involved in prostanoid biosynthesis that in humans is encoded by the PTGIS gene. This enzyme belongs to the family of cytochrome P450 isomerases.
This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. However, this protein is considered a member of the cytochrome P450 superfamily on the basis of sequence similarity rather than functional similarity. This endoplasmic reticulum membrane protein catalyzes the conversion of prostaglandin H<sub>2</sub> to prostacyclin (prostaglandin I<sub>2</sub>), a potent vasodilator and inhibitor of platelet aggregation. An imbalance of prostacyclin and its physiological antagonist thromboxane A<sub>2</sub> contribute to the development of myocardial infarction, stroke, and atherosclerosis.
Unlike most P450 enzymes, PGIS does not require molecular oxygen (O<sub>2</sub>). Instead it uses its heme cofactor to catalyze the isomerization of prostaglandin H<sub>2</sub> to prostacyclin. Prostaglandin H<sub>2</sub> is produced by cyclooxygenase in the first committed step of prostaglandin biosynthesis.
The systematic name of this enzyme class is (5Z,13E)-(15S)-9alpha,11alpha-epidioxy-15-hydroxyprosta-5,13-dienoate 6-isomerase. Other names in common use include prostacyclin synthase, prostacyclin synthetase, prostagladin I<sub>2</sub> synthetase, PGI<sub>2</sub> synthase, PGIS, PTGIS, and PGI<sub>2</sub> synthetase.
Generally, proteinâÂÂprotein interactions play crucial roles and are critical for formation of protein microenvironment, cell signaling and direct regulation of the activity of metabolic enzymes. Information on tissue-specific spectrum of molecular interactions of prostacyclin synthase will be useful for subnetwork analysis of PTGIS. Following proteins became known as potential direct binders of PTGIS: CYP2J2, GST, GSTA1, GLRX3, AKR1A1. ProteinâÂÂprotein and protein-peptide interactions were experimentally verified using surface plasmon resonance technology.