Tungsten and Molybdenum Oxotransferases

本研究的目的是从Mo/W配位环境和钼蝶苷组分的性质和性质方面探讨钼蝶苷和W-pterin中心的结构和功能多样性。该方法包括使用三种互补的光谱技术，即使在存在额外的顺磁性或显色性假基的情况下，也能够选择性地监测Mo/W-pterin中心的电子、磁性和振动特性。Mo(V)和W(V)形式的基态和激发态电子性质将通过变温磁圆二色性和电子顺磁共振光谱来确定。Mo/W配体和钼钼酸盐拉伸模式的振动频率将通过共振拉曼光谱研究，利用激发进入可见电荷转移带；电子和振动分配将基于共振激发谱、同位素位移和适当的Mo/W模型配合物的研究。光谱研究将集中在五种不同类型的氧转移酶上：肝亚硫酸盐氧化酶，来自球状红杆菌的DMSO还原酶，来自热醋酸梭菌的甲酸脱氢酶，来自超嗜热古高温球菌和ES-4的醛铁氧还蛋白氧化还原酶，来自超嗜热古高温球菌和litoralis的甲醛铁氧还蛋白氧化还原酶。氧转移酶催化多种氧的插入/去除反应，在碳、氮和硫的代谢中起着至关重要的作用。在环境温度下工作的中温生物（植物、细菌和哺乳动物）中，许多这些反应是由具有未知结构的新型钼酸盐活性位点的酶催化的。最近对深海火山口的超嗜热古细菌的研究表明，在活性位点上存在类似的酶，这些酶似乎是嗜热酶的进化祖先。本研究的目的是从钼钨配位环境和蝶呤成分的性质和性质等方面探讨钼黄酮和钨黄酮氧转移酶的结构和功能多样性。该方法涉及使用三种互补的光谱技术，能够选择性地监测钼黄酮和钨黄酮辅因子的电子、磁性和振动特性。钼(V)和钨(V)形式的基态和激发态电子性质将通过变温磁圆二色性和电子顺磁共振光谱来确定。金属配体和翼虫蛋白拉伸模式的振动频率将通过共振拉曼光谱研究，利用激发到可见电荷转移带。电子和振动分配将基于共振激发剖面，同位素位移，以及适当的钼和钨模型配合物的研究。这些结果对于理解这类酶的催化机制非常重要，并且可能具有重要的进化和生物技术意义。＊＊＊

9419019 Johnson The objective of this research is to investigate the structural and functional diversity of Mo-pterin and W-pterin centers in terms of Mo/W coordination environment and the nature and properties of the molybdopterin component. The approach involves the use of three complementary spectroscopic techniques that are capable of selectively monitoring the electronic, magnetic and vibrational properties of the Mo/W-pterin centers even in the presence of additional paramagnetic or chromophoric prosthetic groups. Ground and excited state electronic properties for Mo(V) and W(V) forms will be established by variable temperature magnetic circular dichroism and electron paramagnetic resonance spectroscopies. Vibrational frequencies for Mo/W-ligand and molybdopterin stretching modes will be investigated by resonance Raman spectroscopy using excitation into visible charge transfer bands/ Electronic and vibrational assignments will be based on resonance excitation profiles, isotope shifts, and studies of appropriate Mo/W model complexes. Spectroscopic studies will focus on five distinct classes of oxotransferases: hepatic sulfite oxidase, DMSO reductase from Rhodobacter sphaeroides, formate dehydrogenase from Clostridium thermoaceticum, aldehyde ferredoxin oxidoreductases from the hyperthermophilic archaea Pyrococcus furiosus and ES-4, formaldehyde ferredoxin oxidoreductases from the hyperthermophilic archaea Pyrococcus furiosus and Thermococcus litoralis. %%% Oxotransferases catalyze a diverse array of oxygen insertion/removal reactions that are of crucial importance in the metabolism of carbon, nitrogen and sulfur. In mesophilic organisms that function at ambient temperatures (plants, bacteria and mammals), many of these reactions are catalyzed by enzymes with a novel molybdopterin active site of unknown structure. Recent studies of hyperthermorphilic archaea from deep sea volcanic vents have revealed the presence of similar enzymes with tungstopteri n active sites, that appear to be evolutionary ancestors of the mesophilic enzymes. The objective of this research is to investigate the structural and functional diversity of molybdopterin and tungstopterin oxotransferases in terms of molybdenum/tungsten coordination environment and the nature and properties of the pterin component. The approach involves the use of three complementary spectroscopic techniques that are capable of selectively monitoring the electronic, magnetic and vibrational properties of the molybdopterin and tungstopterin cofactors. Ground and excited state electronic properties for molybdenum(V) and tungsten(V) forms will be established by variable temperature magnetic circular dichroism and electron paramagnetic resonance spectroscopies. Vibrational frequencies for metal-ligand and pterin stretching modes will be investigated by resonance Raman spectroscopy using excitation into visible charge transfer bands. Electronic and vibrational assignments will be based on resonance excitation profiles, isotope shifts, and studies of appropriate molybdenum and tungsten model complexes. The results will be important in understanding the catalytic mechanisms of this class of enzymes and are likely to have important evolutionary and biotechnological implications. ***