Human Biochemistry, Volume 1 - Murray R. 1993

Bioenergetics and Carbohydrate and Lipid Metabolism
Metabolism of Unsaturated Fatty Acids and Eicosanoids
Eicosanoids

Arachidonate and A number of other C20 Fatty acids with double bonds alternating with methylene groups serve as precursors to Eicosanoids. These physiologically and pharmacologically active compounds include Prostaglandins (PGs), thromboxanes (TXs), and Leukotrienes (LTs) (see Ch. 15). Arachidonate, which is typically located at the C-2 position of Cell/33.html">Plasma Membrane Phospholipids, is released by the action of phospholipase A2 (Fig. 25.5) and acts as a substrate for The Biosynthesis of PG2, TX2, and LT4. The Metabolic pathways of this substrate vary, with the synthesis of Prostanoids (PG2 and TX2) competing for the substrate with the synthesis of LT4. These two pathways are known, respectively, as the cyclooxygenase and lipoxygenase pathways (Fig. 24.5).

Eicosanoids can be divided into three groups (each comprising PGs, TXs, and LTs) depending on their precursors: linoleate, arachidonate, and α-linolenate (Fig. 24.6).



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