Enzymology of Peroxide Dismutation by a Manganese Catalase

植物乳杆菌产生一种具有过氧化氢酶活性的含锰酶，称为伪过氧化氢酶，以区别于血红素过氧化氢酶。伪过氧化氢酶是一种亚基的低聚物，每个亚基含有两个锰原子，经ESR测量显示，它们参与双核簇。在底物过氧化氢存在的情况下，羟胺和氟化物会抑制催化活性。这些特征表明，该酶是绿色植物光合作用出氧中心双核锰酶的近亲和可溶性同源物。卡特博士在底物和氟化物的存在和不存在的情况下结晶了这种酶，导致酶失活和伴随的假体基漂白。晶体衍射到高分辨率，他收集了4.5A分辨率的三维天然晶体强度数据。他现在计划解决晶体结构，并分析它们的反应机制及其与氧演化中心的关系的线索。

Lactobacillus plantarum produces a manganese-containing enzyme with catalase activity, which has been called pseudocatalase to distinguish it from the heme enzyme catalase. Pseudocatalase is an oligomer of subunits each of which contains two manganese atoms which have been shown by ESR measurements to participate in a binuclear cluster. Catalytic activity is inhibited by hydroxylamine and by fluoride in the presence of substrate, hydrogen peroxide. These features suggest that this enzyme is a close relative and a soluble homologue of the binuclear manganese enzyme in the oxygen evolving center of green plant photosynthesis. Dr. Carter has crystallized this enzyme in the presence and absence of a combination of substrate and fluoride that leads to inactivation of the enzyme and attendant bleaching of the prosthetic group. The crystals diffract to high resolution and he has collected three-dimensional native crystal intensity data to 4.5A resolution. He now plans to solve the crystal structures and to analyze them for clues to their reaction mechanism and their relationship to the oxygen evolving center.