Synthesis of Prostaglandins (PG) and Thromboxanes (TX)

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Homo sapiens
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The bioactive prostaglandin (PG) signalling molecules, including PGA2, PGE2, PGF2a, and PGI2 (prostacyclin) are synthesised from arachidonic acid and its products by various prostaglandin synthase type enzymes. Prostaglandin H2 (PGH2) is the starting point for the synthesis of Thromboxanes (TXs) (Buczynski et al. 2009, Vance & Vance 2008). PGs and TXs are collectively known as the prostanoids.
Two enzymes, PTGS1 and 2 (COX1 and 2) both catalyze the two-step conversion of arachidonic acid to PGH2. PTGS1 is constitutively expressed in many cell types while PTGS2 is induced in response to stress and mediates the syntheses of prostaglandins associated with pain, fever, and inflammation. Aspirin irreversibly inactivates both enzymes (though it acts more efficiently on PTGS1), explaining both its antiinflammatory effects and side effects like perturbed gastic acid secretion. Drugs like celecoxib, by specifically inhibiting PTGS2, have a strong anti-inflammatory effect with fewer side effects. These PTGS2-specific drugs, however, probably because of their effects on the balance of prostaglandin synthesis in platelets and endothelial cells, can also promote blood clot formation (Buczynski et al. 2009; Stables & Gilroy 2011).
Literature References
PubMed ID Title Journal Year
20655950 Old and new generation lipid mediators in acute inflammation and resolution

Stables, MJ, Gilroy, DW

Prog. Lipid Res. 2011
  Biochemistry of Lipids, Lipoproteins and Membranes, 5th Edition

Vance, JE, Vance, DE

19244215 Thematic Review Series: Proteomics. An integrated omics analysis of eicosanoid biology

Dumlao, DS, Buczynski, MW, Dennis, EA

J Lipid Res 2009
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