Characterization of the murine epidermal 12/15-lipoxygenase.

The murine lipoxygenase (LO) family consists of at least seven members classified according to the HETE (hydroxyeicosatetraenoic acid) metabolite generated during arachidonic acid metabolism and the site of tissue expression. At present there are four 12-lipoxygenases that are functionally distinct, vary in cell and tissue distribution, catalytic activity and each are products of separate, linked genes. They are "platelet-type" 12-LO (P-12LO), "leukocyte-type" 12-LO (L-12LO), "epidermal-type" 12-LO (e-12LO) and the most recently discovered 12(R)-LO. In this report we characterize e-12LO, which was overexpressed in the baculovirus/insect cell expression system. The enzyme functions as a dual specificity 12/15-lipoxygenase with a 12-HETE/15-HETE product ratio of approximately 6:1 with arachidonic acid as substrate. Several other polyunsaturated fatty acids served as substrates for e-12LO such as gamma-linolenic, dihomo-gamma-linolenic and eicosapentaenoic acids. A green fluorescent protein/e-12LO fusion protein was localized to the cytosol of transfected HEK 293 cells. The e-12LO gene was expressed in mouse oocytes and early embryos. Western blot analysis revealed high level expression in postnatal day 3 mouse epidermal lysates. Together these data suggest that e-12LO plays a role in normal epidermal function and as yet an undiscovered role in early development.