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C20 prostanoid biosynthesis

General Background A subclass of eicosanoids, the C20 prostanoids comprise of prostaglandins, thromboxanes and prostacyclins. They are all lipid compounds derived from the ω6 essential fatty acid : ARACHIDONIC_ACID. Every prostanoid contains 20 carbon atoms, with an internal carbon ring structure. Prostaglandins are messenger molecules produced de novo by most tissues and organs, that act in an autocrine or paracrine fashion to mediate both homeostatic and inflammatory reactions. The name prostaglandin derives from the fact that initially it was thought to be present mainly in prostate secretions. E. J. Corey completed the first total syntheses of prostaglandins E2 and F2 in 1969. About this Pathway Cell trauma, cytokines, growth factors or other stimuli activate phospholipase A2 (PLA2). There are many isoforms of PLA2 in the cell but the key player appears to be type IV cytosolic PLA2 which is translocated to the nuclear envelope and endoplasmic reticulum . This causes the release of : ARACHIDONIC_ACID from cell membrane phospholipids. The prostaglandin G/H synthases (cyclooxygenases) catalyzes the conversion of : ARACHIDONIC_ACID to : PROSTAGLANDIN-H2 in two steps. First, two : OXYGEN-MOLECULE molecules form two peroxide linkages and a 5-carbon ring is created near the middle of the fatty acid chain, forming an unstable intermediate prostaglandin G. Next, a single oxygen is shed from one of the peroxide linkages to form : PROSTAGLANDIN-H2. All prostanoids originate from : PROSTAGLANDIN-H2. The effect of non-steroidal anti-inflammatory drugs (NSAIDs) on the synthesis of prostaglandins was discovered by J. R. Vane in 1971. Aspirin, the quintessential NSAID exerts its effects can affect the activities of both : HS01815-MONOMER "COX-1" and : HS01115-MONOMER "COX-2". However, its primary mode of action is the irreversible acetylation of COX-2 which loses the ability to generate prostaglandin intermediates but retains oxygenase activity. Statins mediate S-nitrosylation of COX-2 which has the same effect as aspirin mediated acetylation .

from BIOCYC source record: HUMAN_PWY66-374
Type: pathway
Taxonomic scope
organism-specific biosystem
Homo sapiens

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