MECHANISTIC STUDIES OF DIOXO MOLYBDENUM ENZYMES

对两种二氧代钼酶的机理和光谱进行了研究 提出的，重点是各种形式的酶在 它们的周转过程及其电子结构的表征。 主题酶，二甲基亚砜还原酶(来自红细菌 Shaeroides)和亚硫酸盐氧化酶(取自鸡肝)是 一种独特的催化氧原子转移反应的酶 在他们的活动场所拥有一个MoO2单位。这些酶催化一种 所有生物体中各种基本的代谢反应， 包括人类。氧原子转移的方式是在 然而，人们对这些系统知之甚少，尤其是在比较中。 就目前对血红素作用机制的深入了解而言， 含铜、黄素或蝶呤的酶能催化类似的 反应。拟议研究的主要目标是纠正 缺乏关于这类重要酶的机制信息。 众所周知，与上面提到的其他系统相比， 具有MoO2的酶利用水而不是氧气作为来源 当反应被催化时，被结合到底物中的氧原子 是氧化的反应；这个反应产生而不是消耗 生理上有用的还原当量。当反应被催化时 是还原，还原当量被消耗，氧气 从底物上移走的原子形成水。因此，二氧钼酶 代表了被催化的化学类型的独特解决方案。这个 拟议工作的主要目标是比较和对比 MoO2氧化酶和MoO2的机理和光谱特征 还原酶，以便进一步了解最基本的 这类酶的催化作用的各个方面。

A mechanistic and spectroscopic study of two dioxo molybdenum enzymes is proposed, focusing on the various forms of enzyme encountered in the course of turnover and the characterization of their electronic structure. The subject enzymes, dimethylsulfoxide reductase (from Rhodobacter sphaeroides) and sulfite oxidase (from chicken liver), are members of a unique class of enzyme catalyzing oxygen atom transfer reactions that possess a MoO2 unit in their active sites. These enzymes catalyze a variety of essential metabolic reactions in all living organisms, including man. The manner in which oxygen atom transfer is accomplished in these systems, however, is poorly understood, particularly in comparison to the depth of current understanding of the mechanism of action of heme-, copper-, flavin- or pterin-containing enzymes that catalyze similar reactions. The principal goal of the proposed research is to redress the lack of mechanistic information regarding this important class of enzymes. It is known that, in contrast to the other systems mentioned above, the MoO2-possessing enzymes utilize water rather than dioxygen as the source of the oxygen atom incorporated into substrate when the reaction catalyzed is that of an oxidation; this reaction generates rather than consumes physiologically useful reducing equivalents. When the reaction catalyzed is that of a reduction, reducing equivalents are consumed, and the oxygen atom removed from substrate forms water. The dioxo molybdenum enzymes thus represent a unique solution to the type of chemistry being catalyzed. The primary aims of the proposed work are to compare and contrast the mechanistic and spectroscopic features of a MoO2 oxidase and a MoO2 reductase in order to gain further insight into the most fundamental aspects of catalysis by this class of enzymes.