title: ATP allosterically activates the human 5-lipoxygenase molecular mechanism of arachidonic acid and 5(S)-hydroperoxy-6(E),8(Z),11(Z),14(Z)-eicosatetraenoic acid.
abstract: 5-Lipoxygenase (5-LOX) reacts with arachidonic acid (AA) to first generate 5(S)-hydroperoxy-6(E),8(Z),11(Z),14(Z)-eicosatetraenoic acid [5(S)-HpETE] and then an epoxide from 5(S)-HpETE to form leukotriene A4, from a single polyunsaturated fatty acid. This work investigates the kinetic mechanism of these two processes and the role of ATP in their activation. Specifically, it was determined that epoxidation of 5(S)-HpETE (dehydration of the hydroperoxide) has a rate of substrate capture (Vmax/Km) significantly lower than that of AA hydroperoxidation (oxidation of AA to form the hydroperoxide); however, hyperbolic kinetic parameters for ATP activation indicate a similar activation for AA and 5(S)-HpETE. Solvent isotope effect results for both hydroperoxidation and epoxidation indicate that a specific step in its molecular mechanism is changed, possibly because of a lowering of the dependence of the rate-limiting step on hydrogen atom abstraction and an increase in the dependency on hydrogen bond rearrangement. Therefore, changes in ATP concentration in the cell could affect the production of 5-LOX products, such as leukotrienes and lipoxins, and thus have wide implications for the regulation of cellular inflammation.
authors.affiliation: Department of Chemistry and Biochemistry, University of California , Santa Cruz, California 95064, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Smyrniotis
authors.forename: Shannon R
authors.initials: SR
authors.lastname: Barbour
authors.forename: Zexin
authors.initials: Z
authors.lastname: Xia
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hixon
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Holman
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D000494:Allosteric Regulation; D001094:Arachidonate 5-Lipoxygenase / Q000737:chemistry*; D016718:Arachidonic Acid / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D004789:Enzyme Activation; D004852:Epoxy Compounds / Q000737:chemistry; D006801:Humans; D017572:Leukotriene A4 / Q000737:chemistry; D015289:Leukotrienes / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry; D013237:Stereoisomerism; D014783:Viscosity
chemical_list: D004852:Epoxy Compounds; D017572:Leukotriene A4; D015289:Leukotrienes; D010545:Peroxides; D016718:Arachidonic Acid; C025348:arachidonic acid 5-hydroperoxide; D000255:Adenosine Triphosphate; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium