Human and mouse eLOX3 have distinct substrate specificities: Implications for their linkage with lipoxygenases in skin

Abstract

Genetic and biochemical evidence suggests a functional link between human 12R-lipoxygenase (12R-LOX) and epidermal lipoxygenase-3 (eLOX3) in normal differentiation of the epidermis; LOXderived fatty acid hydroperoxide is isomerized by the atypical eLOX3 into a specific epoxyalcohol that is a potential mediator in the pathway. Mouse epidermis expresses a different complement of LOX enzymes, and therefore this metabolic linkage could differ. To test this concept, we compared the substrate specificities of recombinant mouse and human eLOX3 toward sixteen hydroperoxy stereoisomers of arachidonic and linoleic acids. Both enzymes metabolized R-hydroperoxides 2-3 times faster than the corresponding S enantiomers. Whereas 12R-hydroperoxyeicosatetraenoic acid (12R-HPETE) is the best substrate for human eLOX3 (2.4 sec −1 ; at 30 µM substrate), mouse eLOX3 shows the highest turnover with 8R-HPETE (2.9 sec −1 ) followed by 8S-HPETE (1.3 sec −1 ). Novel product structures were characterized from reactions of mouse eLOX3 with 5S-, 8R-, and 8S-HPETEs. 8S-HPETE is converted specifically to a single epoxyalcohol, identified as 10R-hydroxy-8S,9S-epoxyeicosa-5Z,11Z,14Z-trienoic acid. The substrate preference of mouse eLOX3 and the unique occurrence of an 8S-LOX enzyme in mouse skin point to a potential LOX pathway for the production of epoxyalcohol in murine epidermal differentiation.

Epidermis-Type Lipoxygenase 3 Regulates Adipocyte Differentiation and Peroxisome Proliferator-Activated Receptor γ Activity

“…eLOX3 converts HPETE intermediates into epoxyalcohol fatty acids in a hydroperoxide isomerase reaction. The 12-HPETE-derived epoxyalcohol fatty acids are known as hepoxilins (42,63,65). Hepoxilins are a group of epoxyalcohols derived from hydroperoxy fatty acids.…”

“…Thus, our results suggest that the ADD1-dependent induction of adipocyte differentiation and PPAR␥ ligand production is an artifact of forced ADD1 expression. In contrast to other LOXs, eLOX3 functions as a hydroperoxide isomerase converting dioxygenated fatty acids into hepoxilins (63,65). The absence of others LOXs in 3T3-L1 cells, however, makes eLOX3 a counterintuitive candidate for production of a PPAR␥ ligand during adipogenesis.…”

“…In contrast to previously characterized LOXs, eLOX3 functions as a hydroperoxide isomerase, converting the LOX products hydroperoxyeicosatetraenoic acids (HPETEs) to hepoxilinlike products. Curiously, whereas human eLOX3 prefers 12-HPETEs as substrates, mouse eLOX3 favors 5-and 8-HPETEs although both human and mouse eLOX3 have the capability to isomerize a broad spectrum of HPETEs (63,65). The fact that inactivating mutations in either the 12R-LOX gene or the eLOX3 gene are found in patients suffering from the skin disease nonbullous congenital ichthyosiform erythroderma underscores the requirement for a functioning LOX upstream of eLOX3 in skin (25,62).…”

14S,21R-Dihydroxydocosahexaenoic Acid Remedies Impaired Healing and Mesenchymal Stem Cell Functions in Diabetic Wounds

“…In murine skin wounds, there are other lipoxygenases, including epidermis-type LOX3, 12R-LOX, and 8-LOX as well as 5-LOX from recruited leukocytes (26,30,31,50,(53)(54)(55)(56)(57)(58)(59). However, LOX3, 12R-LOX, 8-LOX, or 5-LOX is unlikely to catalyze DHA 14S-hydroxygenation in skin wounds based on the study conducted by other scientists (52) and ourselves.…”

PPARγ ligand production is tightly linked to clonal expansion during initiation of adipocyte differentiation

“…eLOX3 can convert peroxidized fatty acids originating from arachidonic and linoleic acid ( 42,43 ). These fatty acids are present in phospholipids embedded in cellular membranes.…”