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

利用自行研制的ESR和光学同步测量装置（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)Fe（tpp）Cl被用作血红素-Fe ^<3 +>蛋白质的模型络合物。该复合物显示出Fe（tpp）（OOR）的过氧化物加合物的清楚形成，其是充当几种酶促反应的关键中间体。ESR和吸收光谱显示了其形成的特征。2)用Co ^<3 +>-多胺和Co ^<2 +>-（SB）（SB：Shiff碱）作为双加氧酶的模型，我们研究了邻苯二酚双加氧酶反应的反应机理。前者与邻苯二酚形成二元络合物，然后加入O_2形成三元络合物。在后者中，O_2首先与配合物形成氧加合物，并发生分子内电子转移反应。其次，邻苯二酚作为底物被钴配合物氧化成半醌。3)作为Fe-SOD模型的典型例子，Fe ^<3 +>-EDTA及其类似物与活性氧反应。ESRET结果表明，反应中形成了两种中间产物：一种是侧子型Fe ^&lt;3 +&gt;-O_2 ^^，另一种是Fe ^&lt;2 +&gt;-O_2 ^-。<2->以这些中间体作为反应探针，探讨了SOD的反应机理。

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.