Barrios David A, D'Antonio Jennifer, McCombs Nikolette L, Zhao Jing, Franzen Stefan, Schmidt Andreas C, Sombers Leslie A, Ghiladi Reza A
Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
J Am Chem Soc. 2014 Jun 4;136(22):7914-25. doi: 10.1021/ja500293c. Epub 2014 May 21.
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.
人们发现,来自华丽磷虫的海洋珠蛋白脱卤过氧化物酶-血红蛋白(DHP)可催化单卤代吲哚的H2O2依赖性氧化反应,这是DHP之前未知的一类底物。以5-溴吲哚作为代表性底物,发现主要的单加氧产物是5-溴-2-氧代吲哚和5-溴-3-氧代吲哚啉。同位素标记研究证实,掺入的氧原子仅来源于H2O2,这表明DHP具有一种此前未报道的过氧合酶活性。过氧合酶活性可以从铁离子状态或亚铁氧合状态启动,底物转化率和产物分布相当。研究发现,产物5-溴-3-氧代吲哚啉的前体5-溴-3-氧代吲哚能轻易地将高铁酶还原为亚铁氧合状态,这表明该酶存在一种不寻常的产物驱动还原作用。因此,过氧合酶活性停止后,DHP会恢复到具有活性的珠蛋白亚铁氧合形式。在没有H2O2的情况下,与5-溴-3-氧代吲哚反应,在有氧条件下也会产生高于预期反应化学计量的5,5'-二溴靛蓝,并且O2浓度研究表明有氧气消耗。非酶促和厌氧对照都证实了在催化生成5,5'-二溴靛蓝过程中对DHP和分子氧的需求,这共同表明DHP具有一种新发现的氧化酶活性。