Arachidonate 15-lipoxygenase; characteristics and potential biological significance

Arachidonate 15-lipoxygenase (an n-6 lipoxygenase) has been purified to homogeneity, cloned and expressed and appears to be a highly regulated enzyme showing pronounced tissue specificity. The enzyme is expressed prominently in the reticulocyte where it appears to be under posttranscriptional control and may play a key physiological role in reticulocyte maturation by initiating mitochondrial breakdown. 15-Lipoxygenase is also expressed in significant quantities in airway epithelial cells and eosinophils although no clear role for this enzyme in these cell types has been defined. The enzyme catalyzes the conversion of free arachidonic acid to 15-HPETE, free linoleic acid to 13-HPOD and can also oxygenate polyenoic acids esterified in phospholipids. A number of potential physiological and pathological roles for products of this enzyme have been postulated. These include a physiological role in prolactin secretion from pituitary cells and in the initiation of the acrosome reaction in spermatozoa. An important pathological role in the oxidation of LDL by macrophages has also been proposed, indicating that the enzyme could be a pharmacological target for the treatment of atherosclerosis.