Discovery of a second 15 S -lipoxygenase in humans

Abstract

The lipoxygenase metabolism of arachidonic acid occurs in specific blood cell types and epithelial tissues and is activated in inf lammation and tissue injury. In the course of studying lipoxygenase expression in human skin, we detected and characterized a previously unrecognized enzyme that at least partly accounts for the 15S-lipoxygenase metabolism of arachidonic acid in certain epithelial tissues. The cDNA was cloned from human hair roots, and expression of the mRNA was detected also in prostate, lung, and cornea; an additional 16 human tissues, including peripheral blood leukocytes, were negative for the mRNA. The cDNA encodes a protein of 676 amino acids with a calculated molecular mass of 76 kDa. The amino acid sequence has approximately 40% identity to the known human 5S-, 12S-, and 15S-lipoxygenases. When expressed in HEK 293 cells, the newly discovered enzyme converts arachidonic acid exclusively to 15S-hydroperoxyeicosatetraenoic acid, while linoleic acid is less well metabolized. These features contrast with the previously reported 15S-lipoxygenase, which oxygenates arachidonic acid mainly at C-15, but also partly at C-12, and for which linoleic acid is an excellent substrate. The different catalytic activities and tissue distribution suggest a distinct function for the new enzyme compared with the previously reported human 15S-lipoxygenase.

Inhibition of arachidonic acid metabolism and its implication on cell proliferation and tumour-angiogenesis

“…Formation of 5-oxo-7E,9E,11Z,14Z-eicosatetraenoic acid (5-oxo-7,9,11,14-ETE) is the result of non-enzymatic metabolism [59]. Within the 15-LOX pathway, two isoforms have been identified [ 60 ], where 15-LOX-1 preferentially metabolizes linoleic acid into 13S-hydroxyoctadeca-9Z,11E-dienoic acid (13S-HODE), whilst 15-LOX-2 is mainly responsible for the production of 15S-HETE from 15S-HpETE [61,62].…”

15-Lipoxygenase-2 (15-LOX-2) Is Expressed in Benign Prostatic Epithelium and Reduced in Prostate Adenocarcinoma

“…The sample was evaporated under a stream of nitrogen to remove most of the dichloromethane and methanol, water was added, and the products were recovered by C18 SepPak extraction. 8 The extracts were analyzed by reversedphase HPLC using a Beckman Ultrasphere 5-m ODS column (25 ϫ 0.46 cm) with a solvent of methanol/water/ glacial acetic acid, either 90:10:0.01 (by volume) at a flow rate of 1.1 ml/minute (retention time of 15-HETE was approximately 5 minutes) or 80:20:0.01 at 1.1 ml/minute (retention time of 15-HETE approximately 15 minutes). Unlabeled HETEs (5-, 8-, 9-, 11-, 12-, and 15-HETEs) were added to each sample before HPLC analysis; this permitted an exact determination of the retention times of each HETE product within each individual chromatographic run.…”

Synergistic effect of 15-lipoxygenase 2 and radiation in killing head-and-neck cancer

“…15-LOX-2 oxygenates carbon 15 in arachidonic acid (AA) and is one of the important lipid peroxidizing enzymes that have been linked to carcinogenesis including HNC. [13][14][15] Unlike 15-lipoxygenase 1 (15-LOX-1), 15-LOX-2 has limited tissue distribution and significant substrate preference. 13 15-LOX-2 is mainly expressed in epithelia from prostate, 16 esophagus, 17 head and neck, 18 breast, 19 bladder, 19 lung 19 and skin.…”

“…[13][14][15] Unlike 15-lipoxygenase 1 (15-LOX-1), 15-LOX-2 has limited tissue distribution and significant substrate preference. 13 15-LOX-2 is mainly expressed in epithelia from prostate, 16 esophagus, 17 head and neck, 18 breast, 19 bladder, 19 lung 19 and skin. 13,19 15-LOX-2 preferentially converts AA to 15-S-hydroxyeicosatetraenoic acid (15S-HETE) and metabolizes linoleic acid poorly.…”

“…13 15-LOX-2 is mainly expressed in epithelia from prostate, 16 esophagus, 17 head and neck, 18 breast, 19 bladder, 19 lung 19 and skin. 13,19 15-LOX-2 preferentially converts AA to 15-S-hydroxyeicosatetraenoic acid (15S-HETE) and metabolizes linoleic acid poorly. 15-LOX-2 has been shown to be a tumor suppressor.…”