Strict Regiospecificity of Human Epithelial 15-Lipoxygenase-2 Delineates Its Transcellular Synthesis Potential
| Autor: | Thomas Horn, Theodore R. Holman, Abigail R. Green, Jose Carlos, Jevgenij A. Raskatov, Shannon R. Barbour |
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| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Biochemistry & Molecular Biology Stereochemistry Medical Biochemistry and Metabolomics Biochemistry Article Catalysis Substrate Specificity Medicinal and Biomolecular Chemistry 03 medical and health sciences chemistry.chemical_compound Lipoxygenase Hydroxyeicosatetraenoic Acids Humans Arachidonate 15-Lipoxygenase Enzyme kinetics Transcellular Lipoxin 030102 biochemistry & molecular biology biology Hydroxyeicosatetraenoic acid Substrate (chemistry) Lipid signaling 030104 developmental biology chemistry biology.protein Arachidonic acid Biochemistry and Cell Biology |
| Zdroj: | Biochemistry, vol 55, iss 20 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | Lipoxins are an important class of lipid mediators that induce the resolution of inflammation and arise from transcellular exchange of arachidonic acid (AA)-derived lipoxygenase products. Human epithelial 15-lipoxygenase-2 (h15-LOX-2), the major lipoxygenase in macrophages, has exhibited strict regiospecificity, catalyzing only the hydroperoxidation of carbon 15 of AA. To determine the catalytic potential of h15-LOX-2 in transcellular synthesis events, we reacted it with the three lipoxygenase-derived monohydroperoxy-eicosatetraenoic acids (HPETE) in humans: 5-HPETE, 12-HPETE, and 15-HPETE. Only 5-HPETE was a substrate for h15-LOX-2, and the steady-state catalytic efficiency (kcat/Km) of this reaction was 31% of the kcat/Km of AA. The only major product of h15-LOX-2’s reaction with 5-HPETE was the proposed lipoxin intermediate, 5,15-dihydroperoxy-eicosatetraenoic acid (5,15-diHPETE). However, h15-LOX-2 did not react further with 5,15-diHPETE to produce lipoxins. This result is consistent with the specificity of h15-LOX-2 despite the increased reactivity of 5,15-diHPETE. Density functional theory calculations determined that the radical, after abstracting the C10 hydrogen atom from 5,15-diHPETE, had an energy 5.4 kJ/mol lower than that of the same radical generated from AA, demonstrating the facility of 5,15-diHPETE to form lipoxins. Interestingly, h15-LOX-2 does react with 5S,6R-diHETE, forming LipoxinA4, indicating the gemdiol does not prohibit h15-LOX-2 reactivity. Taken together, these results demonstrate the strict regiospecificity of h15-LOX-2 that circumscribes its role in transcellular synthesis. |
| Databáze: | OpenAIRE |
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