title: Peroxygenase and oxidase activities of dehaloperoxidase-hemoglobin from Amphitrite ornata.
abstract: The marine globin dehaloperoxidase-hemoglobin (DHP) from Amphitrite ornata was found to catalyze the H2O2-dependent oxidation of monohaloindoles, a previously unknown class of substrate for DHP. Using 5-Br-indole as a representative substrate, the major monooxygenated products were found to be 5-Br-2-oxindole and 5-Br-3-oxindolenine. Isotope labeling studies confirmed that the oxygen atom incorporated was derived exclusively from H2O2, indicative of a previously unreported peroxygenase activity for DHP. Peroxygenase activity could be initiated from either the ferric or oxyferrous states with equivalent substrate conversion and product distribution. It was found that 5-Br-3-oxindole, a precursor of the product 5-Br-3-oxindolenine, readily reduced the ferric enzyme to the oxyferrous state, demonstrating an unusual product-driven reduction of the enzyme. As such, DHP returns to the globin-active oxyferrous form after peroxygenase activity ceases. Reactivity with 5-Br-3-oxindole in the absence of H2O2 also yielded 5,5'-Br2-indigo above the expected reaction stoichiometry under aerobic conditions, and O2-concentration studies demonstrated dioxygen consumption. Nonenzymatic and anaerobic controls both confirmed the requirements for DHP and molecular oxygen in the catalytic generation of 5,5'-Br2-indigo, and together suggest a newly identified oxidase activity for DHP.
authors.affiliation: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Barrios
authors.forename: Jennifer
authors.initials: J
authors.lastname: D'Antonio
authors.forename: Nikolette L
authors.initials: NL
authors.lastname: McCombs
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Schmidt
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Sombers
authors.forename: Reza A
authors.initials: RA
authors.lastname: Ghiladi
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008958:Models, Molecular; D010088:Oxidoreductases / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry; D010101:Oxygen Consumption; D010104:Oxygen Radioisotopes; D011077:Polychaeta / Q000201:enzymology*; D011487:Protein Conformation
chemical_list: D006454:Hemoglobins; D007211:Indoles; D010104:Oxygen Radioisotopes; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C022333:peroxygenase; D010100:Oxygen