Background：

Dual cyclooxygenase and peroxidase in the biosynthesis pathway of prostanoids， a class of C20 oxylipins mainly derived from arachidonate， with a particular role in the inflammatory response. The cyclooxygenase activity oxygenates arachidonate (AA， C20:4(n-6)) to the hydroperoxy endoperoxide prostaglandin G2 (PGG2)， and the peroxidase activity reduces PGG2 to the hydroxy endoperoxide PGH2， the precursor of all 2-series prostaglandins and thromboxanes. This complex transformation is initiated by abstraction of hydrogen at carbon 13 (with S-stereochemistry)， followed by insertion of molecular O2 to form the endoperoxide bridge between carbon 9 and 11 that defines prostaglandins. The insertion of a second molecule of O2 (bis-oxygenase activity) yields a hydroperoxy group in PGG2 that is then reduced to PGH2 by two electrons. Similarly catalyzes successive cyclooxygenation and peroxidation of dihomo-gamma-linoleate (DGLA， C20:3(n-6)) and eicosapentaenoate (EPA， C20:5(n-3)) to corresponding PGH1 and