Mechanistic and Structural Studies of Novel Heme-Containing Peroxidases

9604004道森含血红素的过氧化物酶催化有机底物氧化，同时将过氧化氢还原为水。最近从海洋生物中分离出了两种新型的含血红素的过氧化物酶，一种能够将卤素结合到芳香底物中，另一种能够去除卤素。这些酶的性质挑战了目前关于过氧化物酶如何发挥作用的教条：一种是氯化底物，没有硫酸盐的近端配体，另一种是含氧物和脱卤物的卤代芳香族化合物，包括氟代芳烃的脱氟。为了更好地了解这两种血红素过氧化物酶的不同寻常的性质，将进行光谱、结构和机理研究。这些研究将涉及使用磁性圆二色谱、EPR和共振拉曼光谱以及高分辨率结晶学来全面表征这两种酶的金属配位结构和完整的三维结构。他们的作用机制将被广泛研究，包括使用同位素标记的过氧化氢来比较和对比他们的过氧化氢激活机制与那些研究得很好的植物过氧化物酶。从海洋来源中分离出两种能够产生和/或处理含卤代芳香族化合物的新型酶，并将对其进行深入研究，包括确定它们的作用机理和三维结构。第一种酶能够将卤素结合到芳香族底物中，并可能作为工业生物催化剂应用于合成含卤素的芳香族化合物。第二种酶能够从芳香族化合物中去除卤素，并可能在被卤代芳香族化合物污染的水或土壤的生物修复中应用。

9604004 Dawson Heme-containing peroxidases catalyze organic substrate oxidation with concomitant reduction of hydrogen peroxide to water. Two novel heme-containing peroxidases, one able to incorporate halogens into aromatic substrates and the other able to remove them, have recently been isolated from marine organisms and initially characterized. The properties of these enzymes challenge the current dogma of how peroxidases function: one chlorinates substrates without having a thiolate proximal ligand and the other both oxygenates and dehalogenates haloaromatics including the defluorination of fluoroaromatics. To better understand the unusual properties of these two heme peroxidases, spectroscopic, structural and mechanistic investigations will be carried out. These studies will involve the use of magnetic circular dichroism, EPR, and resonance Raman spectroscopy as well as high resolution crystallography to fully characterize the metal coordination structure and complete three dimensional structures of these two enzymes. Their mechanisms of action will be extensively examined including the use of isotopically labelled hydrogen peroxide to compare and contrast their mechanisms of hydrogen peroxide activation with those of the well studied plant peroxidases. Two novel enzymes from marine sources which are capable of generating and/or handling halogen-containing aromatic compounds have been isolated and will be thoroughly investigated including the determination of their mechanism of action and three dimensional structure. The first enzyme is able to incorporate halogens into aromatic substrates and may find applications as an industrial biocatalyst in the synthesis of halogen-containing aromatics. The second enzyme is able to remove halogens from aromatic compounds and is likely to have applications in bioremediation of water or soil contaminated with haloaromatics.