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Study on Metalloenzymes with use of Artificial Supramolecules

人工超分子金属酶的研究

基本信息

批准号：
05453030
负责人：
NARUTA Yoshinori
金额：
$ 4.8万
依托单位：
KYUSHU UNIVERSITY (1994)Okazaki National Research Institutes (1993)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Metalloenzymes play versatile roles in biological systems. Most of them have not well-characterized on their structures and reaction mechanisms. Especially, the instability of the enzymes is the major obstacle to elucidate them. In this research project, we have studied modeling of (1) electron transporting system in cytochrome c_3, and (2) manganesecontaining enzymes involved in oxygen evolving processes : bacterial manganese catalase (Mn-CAT) and oxygen evolving complex (OEC) in PSII of higher plants and cyanobacteria. Athracene-linked porphyrin dimers and tetramer can form the corresponding 'imidazoratesqueezed' complexes, which indicated large antiferromagnetic coupling between the Fe (III) ions and negative shifts on their reduction potential. These compounds are considered to be good models of cytochrome c_3. Next, we studied on the modeling of manganese containing enzymes, which involve manganese catalases and oxygen evolving complex in chloroplast. Both of them have function to evolve O_2. To construct their functional model to mimic the oxygen evolution, we used manganese porphyrins, which were considerably stable at their higher oxidation states and showed characteristic UV-vis spectrum depending upon their oxidation states. In the disproportionation of H_2O_2, we found the optimum Mn-Mn separation to attain high catalase activity to be 4.0 A.Such manganese porphyrin dimers also have catalytic activity on the evolution of O_2 by four-electron oxidation of water. This is the first example of the catalytic oxidation of water with use of manganese complexes possessing structurally well-defined structure.

金属酶在生物系统中发挥着多种作用。大多数化合物的结构和反应机理尚未得到很好的研究。特别是，酶的不稳定性是研究它们的主要障碍。在本研究项目中，我们研究了(1)细胞色素c_3中电子传递系统的建模，(2)高等植物和蓝藻PSII中参与出氧过程的含锰酶：细菌锰过氧化氢酶（Mn-CAT）和出氧复合体（OEC）。蒽键卟啉二聚体和四聚体可以形成相应的“咪唑酸挤压”配合物，这表明Fe （III）离子之间存在较大的反铁磁偶联，其还原电位发生负位移。这些化合物被认为是细胞色素c_3的良好模型。接下来，我们研究了含锰酶的建模，包括叶绿体中锰过氧化氢酶和氧进化复合体。它们都有演化O_2的函数。为了构建模拟氧演化的功能模型，我们使用了锰卟啉，它们在高氧化态下相当稳定，并且根据其氧化态显示出特有的紫外-可见光谱。在H_2O_2歧化反应中，我们发现获得高过氧化氢酶活性的最佳Mn-Mn分离为4.0 A。这种卟啉锰二聚体对水的四电子氧化反应也具有催化活性。这是使用结构明确的锰配合物催化氧化水的第一个例子。