Leukotrienes

Leukotrienes are eicosanoids that were originally isolated from leukocytes and contain three double bonds, which explains how they were named. As shown in Figure 19.32, leukotrienes are formed by a pathway independent of that of forming the prostaglandins and thromboxanes.

The pathway to leukotrienes starts by attack on arachidonate of a lipoxygenase, which adds O 2 to C-5, giving 5-hydroperoxyeicosatetraenoic acid (5-HPETE). A dehydration to give the epoxide coupled with isomerization of double bonds gives leukotriene A 4. Hydrolysis of the epoxide ring yields leukotriene B 4. Transfer of the thiol group of glutathione yields leukotriene C 4. Subsequent modifications of the peptide chain (not shown) yield related compounds, leukotrienes D and E.

See also: Eicosanoids, Prostaglandins, Thromboxanes, Eicosanoid Functions

INTERNET LINKS:

> 1. Eicosanoids

> 2. Prostaglandin and Leukotriene Metabolism