Characterization of Epidermal 12(S) and 12(R) Lipoxygenases

Abstract

Lipoxygenases (LO) are a family of non-heme iron containing proteins that stereospecifically insert molecular oxygen into 1, 4-cis, cis-pentadiene containing polyunsaturated fatty acids’. They are generally classified according to their positional specificity of arachidonic acid oxygenation and cell specific expression pattern^2.6. Lipoxygenase activity gives rise to a number of bioactive lipid products including leukotrienes, lipoxins and HETE’s (hydroxyeicosatetraenoic acid’s).⁷’⁸The major lipoxygenase forms include the neutrophil 5-LO, platelet 12-LO and reticulocyte 15LO.2’3’6’9 In recent years the lipoxygenase family has expanded by means of molecular cloning studies to include several new members. An e-12(S)LO (epidermal12(S)lipoxygenase) cDNA was cloned and functionally expressed and its gene isolated¹⁰’¹. Two other lipoxygenases found in skin have also been cloned, a 15-LO in humans distinct from the reticulocyte enzyme⁴and a related phorbol ester inducible 8-LO enzyme in mouse skin^s. All of these lipoxygenases generate HETE metabolites of theS-stereo configuration. However, recently mammalian lipoxygenase cDNAs that generated 12(R) -HETE have been cloned and functionally expressed.^12-14The epidermal 12(S) and 12-(R) lipoxygenases have yet to be characterized in any great detail.^10,12-14Here, we characterize further the epidermal 12(S) and 12(R)-LO’s and attempt to elucidate the enzyme’s primary structural determinants controlling chirality of oxygen insertion.