Conversion of linoleic acid and arachidonic acid by skin epidermal lipoxygenases.

Two different lipoxygenases have been identified in human and rat epidermis. One lipoxygenase has a (n-9)-specificity, converts arachidonic acid into 12-hydroxyeicosatetraenoic acid (12-HETE), and has been described by several investigators. Linoleic acid is not a substrate for this enzyme. The other lipoxygenase, with (n-6)-specificity, converts arachidonic acid into 15-HETE and linoleic acid into 13-hydroxyoctadecadienoic acid (13-HOD). Especially the latter lipoxygenase is thought to be involved in the regulation of the differentiation of the skin cells into a proper water-barrier layer. Linoleate is supposed to be the physiological substrate; this fatty acid is especially present in characteristic sphingolipids with unique structures.