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Photo and Magneto-Chemical Studies on Microstructure and Function of Active Sites

活性位点微观结构和功能的光和磁化学研究

基本信息

批准号：
01470050
负责人：
OHYA Hiroaki
金额：
$ 4.22万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-01470050/
关键词：
Enzymatic Model Enzynatic Reaction Intermediate ESR ESRET Multichannel Photometer SOD Peroxide Adduct 三元錯体

项目摘要

Photo- and magneto-chemical studies on microstructure and function of the active sites in typical enzymes have been carried out by using a simultaneous ESR and optical measurement apparatus (ESRET) developed by this project. 1) Fe (tpp) Cl was employed as a model complexes of heme-Fe^<3+> proteins. This complex showed a clear formation of a peroxide adduct of Fe (tpp)(OOR), which is a key intermediate to function as several enzymatic reaction. The ESR and absorption spectra exhibit characteristic features of its formation. 2) By using the Co^<3+>-polyamine and Co^<2+>-(SB)(SB : Shiff base) as models of dioxygenases we have examined reaction mechanisms of catechol dioxygenase reactions. The former complex formed a binary complex with catechols, followed by an addition of O_2 resulting in a ternary complex. In the latter O_2 first formed an oxygen adduct with the complex, and occurred an intramolecular electron transfer reaction. Secondly, catechol as a substrate was oxydized by the cobalt complex to semiquinone. 3) As a typical example of Fe-SOD model Fe^<3+>-EDTA and its analogs were reacted with active oxygen species. It was found by ESRET that two intermediates are formed : One is sideon type Fe^<3+>-O_2^<2-> and the other Fe^<2+>-O_2^-. By using these intermediates as probes of the recation, the reaction mechanism of the SOD was investigated.

利用本项目研制的同步ESR和光学测量装置(ESRET)，对典型酶活性中心的微观结构和功能进行了光化学和磁化学研究。1)以Fe(TPP)Cl作为血红素-Fe~(2+)&lt；~(3+)-Gt~(2+)蛋白质的模型配合物。该络合物清楚地形成了Fe(TPP)(OOR)的过氧化加合物，该加合物是几种酶反应的关键中间体。ESR和吸收光谱显示了其形成的特征。2)以Co^&lt；3+-多胺和Co^-lt；2+-gt；(Sb)(Sb：Shiff碱)为双加氧酶模型，研究了邻苯二酚双加氧酶的反应机理。前者与儿茶酚形成二元络合物，后加入O2形成三元络合物。在后者中，O2首先与络合物形成氧加合物，并发生分子内电子转移反应。其次，以邻苯二酚为底物，钴络合物将其氧化成半喹酮。3)作为Fe-SOD模型的一个典型例子，Fe~(2+)&lt；~(3+)&gt；-EDTA及其类似物与活性氧物种发生了反应。ESRET研究发现，形成了两种中间体：一种是侧式Fe^&lt；3+&gt；-O_2^&lt；2-&gt；另一种是Fe^&lt；2+&gt；-O_2^-。以这些中间体作为反应的探针，探讨了超氧化物歧化酶的反应机理。