Fig. 1.
Prostaglandin synthesis pathway. A: cyclooxygenase is a heme-containing glycoprotein and is a key enzyme in prostanoid biosynthesis by catalyzing the conversion of arachidonic acid to PGH2. Subsequently, PGH2 is converted to active prostanoids via secondary prostanoid synthases. Prostacyclin has a half-life of ∼1 h before inactivation via a nonenzymatic hydration to form 6-keto-PGF1α. B: 6-keto-PGF1α is further metabolized in urine to form the 2,3-dinor derivative 2,3-dinor-6-keto-PGF1α.