title: Arachidonate 15-lipoxygenase in human corneal epithelium and 12- and 15-lipoxygenases in bovine corneal epithelium: comparison with other bovine 12-lipoxygenases.
abstract: Lipoxygenases of bovine and human corneal epithelia were investigated. The bovine epithelium contained an arachidonate 12-lipoxygenase and a 15-lipoxygenase. The 12-lipoxygenase was found in the microsomal fraction, while the 15-lipoxygenase was mainly present in the cytosol (100,000 x g supernatant). 12S-Hydroxyeicosatetraenoic acid (12S-HETE) and 15S-hydroxyeicosatetraenoic acid (15S-HETE) were identified by GC-MS and chiral HPLC. BW A4C, an acetohydroxamic acid lipoxygenase inhibitor, reduced the biosynthesis of 12S-HETE and 15S-HETE by over 90% at 10 microM. IC50 for the 12-lipoxygenase was 0.3 microM. The bovine corneal 12-lipoxygenase was compared with the 12-lipoxygenases of bovine platelets and leukocytes. All three enzymes metabolized 14C-labelled linoleic acid and alpha-linolenic acid poorly (5-16%) in comparison with [14C]arachidonic acid. [14C]Docosahexaenoic acid and [14C]4,7,10,13,16-docosapentaenoic acid appeared to be less efficiently converted by the corneal enzyme than by the platelet and leukocyte enzymes. Immunohistochemical analysis of the bovine corneal epithelium using a polyclonal antibody against porcine leukocyte 12-lipoxygenase gave positive staining. The cytosol of human corneal epithelium converted [14C]arachidonic acid to one prominent metabolite. The product co-chromatographed with 15S-HETE on reverse phase HPLC, straight phase HPLC and chiral HPLC. Our results suggest that human corneal epithelium contains a 15-lipoxygenase and that bovine corneal epithelium contains both a 15-lipoxygenase and a 12-lipoxygenase. The corneal 12-lipoxygenase appears to differ catalytically from earlier described bovine 12-lipoxygenases.
authors.affiliation: Department of Pharmaceutical Biosciences, Uppsala University Biomedical Centre, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Liminga
authors.forename: L
authors.initials: L
authors.lastname: Hörnsten
authors.forename: H W
authors.initials: HW
authors.lastname: Sprecher
authors.forename: E H
authors.initials: EH
authors.lastname: Oliw
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000032:analysis*; D001093:Arachidonate 15-Lipoxygenase / Q000032:analysis*; D016718:Arachidonic Acid / Q000378:metabolism; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003315:Cornea / Q000201:enzymology*; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis; D007150:Immunohistochemistry; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase