Synthetic Modeling of Copper Protein Active Sites

描述（由申请人提供）：铜在许多环境和生物重要过程中起着关键作用，特别是当被包裹在自然界中广泛分布的酶中时。酶活性位点上的铜离子具有多种重要功能，包括结合和激活双氧（O2）以影响代谢重要的化学反应，以及在全球氮循环中重要的微生物呼吸过程中氧化含氮化合物（如亚硝酸盐和氧化亚氮（N2O））的还原。尽管进行了广泛的研究，但有关这些过程的详细分子水平途径的许多问题仍未得到解答。本文描述的研究通过综合建模方法解决了其中的一些问题。在这种方法中，设计了低分子量复合物来复制铜酶活性位点的结构和功能，并对其反应性进行了研究。目标是发展对与生物系统相关的几何、电子结构、键合和反应机制的详细理解。特别是，该研究旨在详细了解含铜酶的一个重要子集在O2和N2O的结合和激活中的基本化学作用。这一目标将通过三个具体目标来解决：(1)单铜位点的双氧激活，(2)多铜位点的双氧激活，以及(3)铜硫化学模拟氧化亚氮还原酶的CuZ位点。在目的(1)和(2)中，将制备高活性的单铜和多铜氧化物质的合成类似物，以评估它们在结合和激活O2的酶中的可能作用。在目的(3)中，将合成一种新的多铜(I)-硫化物模型，该模型是在一种重要的环境酶——氧化亚氮还原酶中发现的罕见的四铜-硫化物簇（CuZ），并研究它们与N2O的反应性。除了渴望深入了解铜酶的结构/功能关系外，提出的工作旨在开发具有基础意义的新型铜化学。公共卫生相关性：该研究旨在详细了解一组重要含铜酶在O2和N2O结合和活化过程中的基本化学作用。二氧激活酶参与了对生命至关重要的大量生物过程，包括呼吸、金属离子稳态（其破坏导致疾病）、重要有机代谢物、激素和对人类健康至关重要的神经递质的产生。微生物酶氧化亚氮还原酶对N2O的还原将这种温室气体转化为惰性的N2，这一过程被认为是全球氮循环的关键组成部分，因此与公众健康直接相关。

DESCRIPTION (provided by applicant): Copper plays a key role in numerous environmentally and biologically important processes, particularly when encapsulated within enzymes that are widely distributed in Nature. The copper ions in the active sites of enzymes perform a variety of significant functions, including the binding and activation of dioxygen (O2) for effecting metabolically significant chemical reactions and the reduction of oxidized nitrogen-containing compounds like nitrite and nitrous oxide (N2O) during microbial respiratory processes important within the global nitrogen cycle. Despite extensive research, many questions remain unanswered concerning the detailed molecular level pathways of these processes. The research described herein addresses some of these questions through the synthetic modeling approach. In this approach, low molecular weight complexes designed to replicate aspects of copper enzyme active site structure and function are characterized and their reactivity studied. The goals are to develop detailed understanding of geometries, electronic structures, bonding, and reaction mechanisms relevant to the biological systems. In particular, the research aims to provide detailed understanding of the fundamental chemistry underlying the function of an important subset of copper-containing enzymes involved in the binding and activation of O2 and N2O. This objective will be addressed through three specific aims: (1) Dioxygen Activation at Monocopper Sites, (2) Dioxygen Activation at Multicopper Sites, and (3) Copper-Sulfur Chemistry for Modeling the CuZ Site of Nitrous Oxide Reductase. In aims (1) and (2), synthetic analogs of highly reactive mono- and multicopper oxidizing species will be prepared in order to evaluate their possible role in enzymes that bind and activate O2. In aim (3), new multicopper(I)-sulfide models of the unusual tetracopper-sulfide cluster (CuZ) found in an environmentally important enzyme, nitrous oxide reductase, will be synthesized and their reactivity with N2O will be studied. In addition to aspiring to a deep understanding of copper enzyme structure/function relationships, the proposed work is aimed at developing novel copper chemistry of fundamental significance. PUBLIC HEALTH RELEVANCE: The research aims to provide detailed understanding of the fundamental chemistry underlying the function of an important subset of copper-containing enzymes involved in the binding and activation of O2 and N2O. The dioxygen-activating enzymes are involved in a plethora of important biological processes central to life, including respiration, metal ion homeostasis (the disruption of which causes disease), and the production of important organic metabolites, hormones, and neurotransmitters essential to human health. The reduction of N2O by the microbial enzyme nitrous oxide reductase converts this greenhouse gas to inert N2 in a process recognized to be a critical component of the global nitrogen cycle and thus directly relevant to public health.