What is Arachidonic Acid?
Arachidonic acid (AA, sometimes ARA) is an omega-6 fatty acid 20:4(ù-6). It is the counterpart to the saturated arachidic acid found in peanut oil.
Chemistry:
In chemical structure, arachidonic acid is a carboxylic acid with a 20-carbon chain and four cis double bonds; the first double bond is located at the sixth carbon from the omega end.
Some chemistry sources define 'arachidonic acid' to designate any of the eicosatetraenoic acids. However, almost all writings in biology, medicine and nutrition limit the term to all-cis 5,8,11,14-eicosatetraenoic acid.
Biology:
Arachidonic acid is a polyunsaturated fatty acid that is present in the phospholipids (especially phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositides) of membranes of the body's cells, and is abundant in the brain.
It is also involved in cellular signaling as a second messenger.
It is the source of several other molecules with specific roles, as described in the next section.
Synthesis and cascade:
Eicosanoid synthesis.Arachidonic acid is freed from phospholipid molecule by the enzyme phospholipase A2, which cleaves off the fatty acid.
Arachidonic acid is a precursor in the production of eicosanoids:
the enzymes cyclooxygenase and peroxidase lead to Prostaglandin H2, which in turn is used to produce the prostaglandins, prostacyclin, and thromboxanes.
the enzyme 5-lipoxygenase leads to 5-HPETE, which in turn is used to produce the leukotrienes.
arachidonic acid is also used in the biosynthesis of anandamide.
The production of these derivatives and their action in the body are collectively known as the arachidonic acid cascade; see essential fatty acid interactions for more details.
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