MECHANISTIC STUDIES OF DIOXO MOLYBDENUM ENZYMES

两种二氧钼酶的机理和光谱研究 提出，集中在各种形式的酶中遇到的 的周转过程和表征其电子结构。 本发明的酶，二甲基亚砜还原酶（来自Rhodobacter sphaeroides）和亚硫酸盐氧化酶（来自鸡肝），是一个 一类独特的酶催化氧原子转移反应， 在它们的活性部位具有MoO 2单元。这些酶催化 所有生物体中的各种基本代谢反应， 包括人类。氧原子转移的方式是在 然而，人们对这些系统的了解很少，特别是与 到目前对血红素作用机制的理解的深度， 含铜、黄素或蝶呤的酶催化类似的 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理信息。 已知的是，与上述其他系统相比， 具有MoO 2的酶利用水而不是分子氧作为来源 当反应催化时， 是一种氧化反应;这种反应产生而不是消耗 生理上有用的还原当量。当反应催化 是还原的过程，还原当量被消耗，氧气 从衬底上除去的原子形成水。因此，二氧钼酶 代表了被催化的化学类型的独特解决方案。的 拟议工作的主要目的是比较和对比 MoO 2氧化酶和MoO 2的机理和光谱特征 还原酶，以进一步了解最基本的 这类酶的催化作用。

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.