Klabunde T, Eicken C, Sacchettini J C, Krebs B
Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA.
Nat Struct Biol. 1998 Dec;5(12):1084-90. doi: 10.1038/4193.
Catechol oxidases are ubiquitous plant enzymes containing a dinuclear copper center. In the wound-response mechanism of the plant they catalyze the oxidation of a broad range of ortho-diphenols to the corresponding o-quinones coupled with the reduction of oxygen to water. The crystal structures of the enzyme from sweet potato in the resting dicupric Cu(II)-Cu(II) state, the reduced dicuprous Cu(I)-Cu(I) form, and in complex with the inhibitor phenylthiourea were analyzed. The catalytic copper center is accommodated in a central four-helix-bundle located in a hydrophobic pocket close to the surface. Both metal binding sites are composed of three histidine ligands. His 109, ligated to the CuA site, is covalently linked to Cys 92 by an unusual thioether bond. Based on biochemical, spectroscopic and the presented structural data, a catalytical mechanism is proposed in which one of the oxygen atoms of the diphenolic substrate binds to CuB of the oxygenated enzyme.
儿茶酚氧化酶是普遍存在于植物中的酶，含有双核铜中心。在植物的伤口反应机制中，它们催化多种邻二酚氧化为相应的邻醌，同时将氧气还原为水。分析了来自甘薯的该酶处于静止二价铜Cu（II）-Cu（II）状态、还原的亚铜Cu（I）-Cu（I）形式以及与抑制剂苯基硫脲形成复合物时的晶体结构。催化铜中心位于靠近表面的疏水口袋中的中央四螺旋束中。两个金属结合位点均由三个组氨酸配体组成。与CuA位点相连的His 109通过一个不寻常的硫醚键与Cys 92共价连接。基于生化、光谱学和所呈现的结构数据，提出了一种催化机制，其中二酚底物的一个氧原子与氧化酶的CuB结合。
