Physicochemical and Structural Analysis fo Functions of Quinonoid Cofactors and Quinoproteins

1从氧化还原反应、酸碱反应和半喹自由基电子结构的角度，对辅酶细菌甲胺脱氢酶色氨酸色氨酸的理化性质和光谱性质进行了研究。还考察了TTQ对底物类似物氨的反应性。这些物理化学性质和结构性质的意义与其在酶反应中的作用有关。2.为了获得苯二酚及其相关分子的光谱电化学性质，我们发展了柱-电解光谱学。该方法已成功地应用于藜麦血红蛋白乙醇脱氢酶五步电子转移的热力学分析。3合成了铜胺氧化酶的辅因子Topa-Q的几个模型化合物。用ttq和tpq模型化合物以及吡咯啉…对苯醌催化的胺氧化反应进行了详细的动力学分析。较多的苯二酚(PQQ)。用电子自旋共振波谱表征了催化反应过程中生成的反应中间体自由基。这些结果有力地支持了转氨基反应的机理。4邻苯二酚的催化活性与电子结构之间的关系表明邻苯二酚结构在催化胺氧化活性的表达中具有重要意义。与TTQ和PQQ作为严格的邻苯二酚相比，游离的TPQ模型化合物在邻苯二酚型和对苯二酮型电子结构之间的互变异构化导致了它们在胺氧化中的催化活性相对较低。5在这些结果的基础上，提出了铜(II)在铜胺氧化酶中作为瞬时分子内电子受体的作用，通过生成亚氨基-TPQ半喹酮来增强对氧的反应活性，并在含有TPQ的胺氧化酶中作为弱配体，使TPQ辅因子具有邻苯二酮型电子结构。较少

1 Physicochemical and spectroscopic properties of tryptophan tryptophylquinone (TTQ), a cofactor bacterial methylamine dehydrogenase, have been elucidated in view of redox and acid-base reactions and semiquinone radical electronic structure. Reactivity of TTQ toward ammonia, as a substrate analog, has been also investigated. Significance of these physicochemical and structural properties have been detailed in relation with its function in the enzymatic reaction.2 Column-electrolytic spectroscopy has been developed in order to obtain spectroelectrochemical property of quinones and related molecules. This method has been successfully applied to the thermodynamic analysis of the five-step electron transfer of a quinohemoprotein, alcohol dehydrogenase.3 Several model compounds of topa quinone, a cofactor of copper amine oxidases, were synthesized. Detailed kinetic analysis has been performed concerning quinone-catalyzed amine oxidation using TTQ and TPQ model compounds as well as pyrroloqu … More inoline quinone (PQQ). A reaction intermediate radical generated during the catalytic reaction has been characterized using electron spin resonance spectroscopy. All these results strongly support a transamination mechanism.4 Relation between the catalytic activity and electronic structure of quinones suggests the significance of ortho-quinone structures in expression of the catalytic amine oxidation activity. Tautomerization of free TPQ model compounds between ortho-and para-quinone-type electronic structures is responsible for their relatively low catalytic activity in the amine oxidation compared with TTQ and PQQ as rigorous ortho-quinones. On the other hand, it has been found that semiquinone radicals participates is autoxidation of reduced quinones.5 On the basis of these results, roles of Cu (II) is proposed as a transient intramolecular electron acceptor in copper amine oxidases to enhance the reactivity toward dioxygen through the generation of the imino-TPQ semiquinone and as a weak ligand in TPQ-containing amine oxidases to make the TPQ cofactor to bear an ortho-quinone-type electronic structure. Less