NON-HEME IRON OXYGEN ACTIVATION IN ENZYMES AND MODELS

生物系统中分子氧的激活是一个重大问题 重要性，因为它参与许多代谢过程。 虽然血红素系统中的氧活化机制， 细胞色素P450和过氧化物酶变得相当好理解， 对非血红素系统的相应机制知之甚少。 这些 后一种酶参与芳香族和脂肪族代谢，胶原蛋白 形成，神经化学物质和抗生素的合成，并参与 在从芳环的氧化裂解， 脂族和芳族羟基化，环化，包括 杂原子 对于许多单核非血红素铁酶， O2仅在底物或辅因子与活性位点相互作用后发生 铁，例如儿茶酚双加氧酶的儿茶酚， 异青霉素N合酶和脯氨酰的α-酮酸辅因子 羟化酶、棒氨酸合酶和其它α-酮戊二酸依赖性 加氧酶 建议采用一种通用机制， 这些酶的化学性质，但双氧活化步骤的细节 由于底物的不同性质而与酶不同，和/或 辅因子 重要的问题包括，1）O2是如何被这些激活的 酶，和2）什么是高价中间体的性质， 参与反应？ 光谱（NMR、EPR、共振拉曼、穆斯堡尔、EXAFS）和机理 建议对许多酶进行研究，以阐明 活性中心结构和作用机制。 这些包括内二醇 切割儿茶酚双加氧酶，异青霉素N合酶，p- 羟苯丙酮酸双加氧酶和棒氨酸合酶（酮酸- 依赖酶）。 模型复合物将被合成并用作模型 来解释酶的光谱特征。 更重要的是 将模拟氧化的关键机械步骤。 领域 特别感兴趣的是：1）儿茶酚的仿生氧化裂解，2） 异青霉素N合酶和α- 酮酸依赖性加氧酶反应，3）瞬时的表征 高价中间体。 与过去一样， 生物化学和无机方面的建议是重要的 方案的成功。

The activation of dioxygen in biological systems is a question of great importance because of its involvement in many metabolic processes. Although the mechanism of oxygen activation in heme systems such as cytochrome P450 and peroxidases is becoming quite well understood, much less is known of the corresponding mechanisms for non-heme systems. These latter enzymes are involved in aromatic and aliphatic metabolism, collagen formation, the synthesis of neurochemicals and antibiotics, and participate in reactions that range from oxidative cleavage of aromatic rings, aliphatic and aromatic hydroxylation, to ring cyclizations involving heteroatoms. For many mononuclear nonheme iron enzymes, the reaction with O2 occurs only after substrate or cofactor interacts with the active site iron, e.g. catechol for catechol dioxygenases, substrate thiol for isopenicillin N synthase, and the alpha-ketoacid cofactor for prolyl hydroxylase, clavaminate synthase and other alpha-ketoglutarate-dependent oxygenases. It is proposed that a common general mechanism unites the chemistry of these enzymes, but the details of the dioxygen activation step vary from enzyme because of the divergent natures of the substrates and/or cofactors. Important questions include, 1) how is O2 activated by these enzymes, and 2) what is the nature of high valent intermediates that are involved in the reactions? Spectroscopic (NMR, EPR, resonance Raman, Mossbauer, EXAFS) and mechanistic studies are proposed for a number of enzymes to elucidate details of the active site structure and the mechanism of action. These include intradiol cleaving catechol dioxygenases, isopenicillin N synthase, p- hydroxyphenylpyruvate dioxygenase, and clavaminate synthase (ketoacid- dependent enzymes). Model complexes will be synthesized and used as models to interpret spectroscopic features of the enzymes. More importantly, the key mechanistic steps of the oxidations will be modeled. Areas of particular interest are: 1) biomimetic oxidative cleavage of catechols, 2) development of models for the isopenicillin N synthase and the alpha- ketoacid-dependent oxygenase reactions, 3) characterization of transient high valent intermediates. As in the past, the synergistic interaction of the biochemical and inorganic aspects of the proposal is important for the success of the program.