Multinuclear Dioxygen-Utilizing Copper Enzymes: Diverse Roles for Aromatic Redox Active Amino Acids

项目摘要 地球上的有氧生物通过各种各样的方式利用分子氧（O2）的氧化能力。 酶辅因子，并利用高氧化电位介导许多氧化转化 在代谢功能中。这些辅因子中的许多是由两个金属中心组成的偶联双核位点 例如铜和铁紧密接触。该提案详细介绍了以下领域的基础研究： 生物无机化学，旨在解决几个有趣的问题，氧化还原的潜在作用， 芳香族活性氨基酸如酪氨酸和色氨酸链在酶的作用机制和功能。 我们确定了三种不同类型的O2利用铜酶，包括细胞色素c氧化酶（CcO） 将氧气还原成水，多铜氧化酶（MCO）将该反应与四个单电子 氧化的底物，和一类新的铜酶称为BURP结构域环化酶，催化 2-肽底物中Tyr/Trp链的电子氧化大环化。 除了BURP结构域之外，在这些酶中已经建立了底物或末端电子受体 这些酶还有待证实。 在所有三类中，适当调节和定位的Tyr/Trp链作为一种或多种酶发挥不同的作用。 活性部位的组成部分（即，CcO），或者他们可以被指定为调解角色，以提供替代方案 更难处理的衬底的氧化路径（即，MCO）。它们甚至可以作为直接底物， 活性位点（即，Cu依赖性BURP结构域环化酶）。在所有情况下，尽管使用这些不同的 链，它们的主要功能是微妙地提供O2还原所需的电子/质子。这些是怎么 为特定功能设计/优化的残基？这些之间有什么异同 酵素？我们的研究旨在揭示这些Tyr/Trp链在酶功能中的潜在作用， 机制，并解决一些问题，铜的生化和有氧代谢。

PROJECT SUMMARY Aerobic life on earth harnesses the oxidizing power of molecular oxygen (O2) through a diverse range of enzyme cofactors and employs that high oxidation potential to mediate numerous oxidative transformations during metabolic functions. Many of these cofactors are coupled binuclear sites consisting of two metal centers such as copper and iron in close proximity. This proposal details fundamental research in the field of bioinorganic chemistry and aims to address several intriguing questions about the potential roles of redox aromatic active amino acids such as tyrosine and tryptophane chains in the enzyme mechanism and function. We identified three different classes of O2-utilizing copper enzymes including cytochrome c oxidase (CcO) which reduces O2 to water, multicopper oxidase (MCO) which couples that reaction to four one-electron oxidations of the substrates, and a new class of copper enzymes called BURP domain cyclases which catalyze 2-electron oxidative macrocyclization of the Tyr/Trp chains in peptide substrates.The use of O2 as either a substrate or terminal electron acceptor has been established in these enzymes except for the BURP domain enzymes which is yet to be confirmed. In all three classes, appropriately tuned and positioned Tyr/Trp chains play different roles either as an integral part of the active site (i.e., CcO) or they may be assigned a mediatory role to provide an alternative path for oxidation of the more challenging substrates (i.e., MCO). They may even act as the direct substrate for the active site (i.e., Cu-dependent BURP domain cyclases). In all cases, despite the diverse use of these chains, their main function is to delicately supply the electron/proton needed for the O2 reduction. How are these residues designed/optimized for a particular function? What are the similarities and differences between these enzymes? Our studies aim to reveal the potential role of these Tyr/Trp chains play in enzymatic function and mechanism and address some of the questions about copper biochemistry and aerobic metabolism.