title: An insight into the regiospecificity of linoleic acid peroxidation catalyzed by mammalian 15-lipoxygenases.
abstract: 15-Lipoxygenases (15-LOs) catalyze the peroxidation reaction of linoleic acid (LA) in mammals producing almost exclusively 13-(S)-hydroperoxyoctadecadienoic acid (13-(S)-HPODE). Although several hypotheses have been formulated, the molecular basis of such enzymatic regiospecificity is unclear. We have here combined quantum mechanics/molecular mechanics (QM/MM) calculations with molecular dynamics simulations to analyze the peroxidation mechanism using a complete rabbit 15-LO-1/LA solvated model. C9 and C13 being equivalent for planarity and spin density, the QM/MM potential energy profiles of the O2 addition to those two atoms were calculated. The difference in the potential energy barrier heights is clear enough to justify that O2 selectively attacks C13 giving 13-(S)-HPODE. Oxygenation at C9 is hindered by two steric-shielding residues (Leu597 and Gln548). The calculated free energy profile at 300 K for the O2 addition to C13 confirms that the peroxidation on C13 is a reversible viable process in agreement with experiments. Thus, the subsequent reduction of the peroxyl radical to give the final hydroperoxidated product is expected to give the irreversibility character to the overall process.
authors.affiliation: Departament de Química and ‡Institut de Biotecnologia i de Biomedicina (IBB), Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
authors.forename: Reynier
authors.initials: R
authors.lastname: Suardíaz
authors.forename: Laura
authors.initials: L
authors.lastname: Masgrau
authors.forename: José M
authors.initials: JM
authors.lastname: Lluch
authors.forename: Angels
authors.initials: A
authors.lastname: González-Lafont
mesh_terms: D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000737:chemistry*; D055162:Biocatalysis; D019787:Linoleic Acid / Q000737:chemistry*; D008041:Linoleic Acids / Q000737:chemistry*; D015227:Lipid Peroxidation; D008054:Lipid Peroxides / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D011817:Rabbits; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D008041:Linoleic Acids; D008054:Lipid Peroxides; C038649:13-hydroperoxy-9,11-octadecadienoic acid; D019787:Linoleic Acid; D001093:Arachidonate 15-Lipoxygenase; D010100:Oxygen