title: A Catalase-related Hemoprotein in Coral Is Specialized for Synthesis of Short-chain Aldehydes: DISCOVERY OF P450-TYPE HYDROPEROXIDE LYASE ACTIVITY IN A CATALASE.
abstract: In corals a catalase-lipoxygenase fusion protein transforms arachidonic acid to the allene oxide 8R,9-epoxy-5,9,11,14-eicosatetraenoic acid from which arise cyclopentenones such as the prostanoid-related clavulones. Recently we cloned two catalase-lipoxygenase fusion protein genes (a and b) from the coral Capnella imbricata, form a being an allene oxide synthase and form b giving uncharacterized polar products (Lõhelaid, H., Teder, T., Tõldsepp, K., Ekins, M., and Samel, N. (2014) PloS ONE 9, e89215). Here, using HPLC-UV, LC-MS, and NMR methods, we identify a novel activity of fusion protein b, establishing its role in cleaving the lipoxygenase product 8R-hydroperoxy-eicosatetraenoic acid into the short-chain aldehydes (5Z)-8-oxo-octenoic acid and (3Z,6Z)-dodecadienal; these primary products readily isomerize in an aqueous medium to the corresponding 6E- and 2E,6Z derivatives. This type of enzymatic cleavage, splitting the carbon chain within the conjugated diene of the hydroperoxide substrate, is known only in plant cytochrome P450 hydroperoxide lyases. In mechanistic studies using (18)O-labeled substrate and incubations in H2(18)O, we established synthesis of the C8-oxo acid and C12 aldehyde with the retention of the hydroperoxy oxygens, consistent with synthesis of a short-lived hemiacetal intermediate that breaks down spontaneously into the two aldehydes. Taken together with our initial studies indicating differing gene regulation of the allene oxide synthase and the newly identified catalase-related hydroperoxide lyase and given the role of aldehydes in plant defense, this work uncovers a potential pathway in coral stress signaling and a novel enzymatic activity in the animal kingdom.
authors.affiliation: From the Department of Chemistry, Tallinn University of Technology, 12618 Tallinn, Estonia, Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, and.
authors.forename: Tarvi
authors.initials: T
authors.lastname: Teder
authors.affiliation: From the Department of Chemistry, Tallinn University of Technology, 12618 Tallinn, Estonia.
authors.forename: Helike
authors.initials: H
authors.lastname: Lõhelaid
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, and.
authors.forename: William E
authors.initials: WE
authors.lastname: Boeglin
authors.affiliation: Department of Biochemistry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Wade M
authors.initials: WM
authors.lastname: Calcutt
authors.affiliation: Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, and.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brash
authors.affiliation: From the Department of Chemistry, Tallinn University of Technology, 12618 Tallinn, Estonia, nigulas.samel@ttu.ee.
authors.forename: Nigulas
authors.initials: N
authors.lastname: Samel
mesh_terms: D000446:Aldehyde-Lyases / Q000235:genetics / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D037421:Anthozoa / Q000201:enzymology* / Q000235:genetics; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015289:Leukotrienes / Q000378:metabolism*; D010103:Oxygen Isotopes; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000447:Aldehydes; D015289:Leukotrienes; D010103:Oxygen Isotopes; D011993:Recombinant Fusion Proteins; C047629:8-hydroperoxyeicosatetraenoic acid; D003577:Cytochrome P-450 Enzyme System; D002374:Catalase; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase
keywords: allene oxide synthase; arachidonic acid (AA) (ARA); catalase; coral; eicosanoid biosynthesis; enzyme mechanism; high performance liquid chromatography (HPLC); hydroperoxide lyase; nuclear magnetic resonance (NMR)