Peroxygenase and Oxidase Activities of Dehaloperoxidase-Hemoglobin from Amphitrite ornata

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• 作者：David A. Barrios ; Jennifer D鈥橝ntonio ; Nikolette L. McCombs ; Jing Zhao ; Stefan Franzen ; Andreas C. Schmidt ; Leslie A. Sombers ; Reza A. Ghiladi
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：June 4, 2014
• 年：2014
• 卷：136
• 期：22
• 页码：7914-7925
• 全文大小：643K
• 年卷期：v.136,no.22(June 4, 2014)
• ISSN：1520-5126

文摘

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鈥?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鈥?Br₂-indigo, and together suggest a newly identified oxidase activity for DHP.