PORPHYRINS AND QUINONES AS ENZYME COFACTORS

描述：在人类和动物中，从血红蛋白中释放的血红素， 肌红蛋白，细胞色素P-450降解转化为开链 胆绿素通过血红素加氧酶（HO）催化。 在这些依赖氧气的 过程中会释放一氧化碳。 大脑中发现HO活性 组织暗示CO是一种神经递质。 一氧化氮合酶 (NOS)还通过催化反应生成双原子气体分子， L-精氨酸转化为瓜氨酸，产物NO是主要的 调节神经、免疫和心血管系统。 目标 本研究项目的重点是阐明O2- 激活和血红素辅因子的催化机制， HO型和NOS型以及用定点突变制备的酶， 探测血红素结构和活性的变化。 这种方法 项目是表征氧化和氧化的中间体的 血红素辅因子的振动光谱，加上一个有力的 使用新型高度保护的金属卟啉的合成模拟方法 其甚至在室温下稳定Fe-O2加合物。 呼吸- 所有有氧生命形式中的耦合能量转换是通过以下方式进行的： 细胞色素氧化酶 细胞色素bd氧化酶。大肠杆菌是一个终端 一种氧化酶，其异常高的O2亲和性与其D 辅因子5，6-二羟基原叶绿素 氢化卟啉的研究 氧化酶将继续使用发色团特异性技术， 共振拉曼光谱。 一个主要目标是确定 辅因子的轴向配体。 对于二氢卟酚d，这项工作旨在 证实了这一提议，即这种辅因子是独一无二的，缺乏强有力的 轴向配体 d辅因子的化学工作将得到支持 一个新的有效的合成模型。 第三个也是不断扩大的方面是， 本研究项目是调查醌的作用， 胺氧化酶中的辅因子。 与卟啉一样，这项工作依赖于 用于光谱比较的准确醌模型化合物。 结缔组织的交联是由铜lysil 氧化酶，一种在其活性位点具有酪氨酸衍生的醌的酶。 拟议的研究将使用拉曼光谱来确定性质 醌取代基在以前未表征的辅因子（如在 lysil氧化酶），在催化循环的中间体中，以及在 辅因子的生物合成。

DESCRIPTION: In humans and animals, the heme released from hemoglobin, myoglobin, and cytochrome P-450 degradation is converted to open-chain biliverdin by heme oxygenase (HO) catalysis. In these O2-dependent processes, carbon monoxide is released. HO activity found in brain tissue has implicated CO as a neurotransmitter. Nitric oxide synthase (NOS) also generates a diatomic gas molecule by catalyzing the conversion of L-arginine to citrulline, and the product NO is a major regulator in the nervous, immune, and cardiovascular systems. A target of this research project is the elucidation of the chemistry of O2- activation and the mechanism of catalysis of the heme cofactors in wild- type HO and NOS and in enzyme prepared with site-directed mutations that probe changes in heme structure and activity. The approaches of this project are to characterize oxygenated and oxidized intermediates of the heme cofactors by vibrational spectroscopy, coupled with a vigorous synthetic model approach using novel, highly protected metallo-porphyrins that even stabilize an Fe-O2 adduct at room temperature. Respiration- coupled energy transduction in all aerobic life forms is carried out by cytochrome oxidases. Cytochrome bd oxidase of E. coli is a terminal oxidase whose unusually high O2 affinity is associated with its d cofactor, a 5,6- dihydroxyprotochlorin. Research on this hydroporphyrin oxidase will be continued using the chromophore-specific technique of resonance Raman spectroscopy. A principal goal is the identification of the axial ligands of the cofactors. For chlorin d, this work seeks to confirm the proposal that this cofactor is unique in lacking a strong axial ligand. Work on the chemistry of the d cofactor will be supported by a new effective synthetic model. A third and expanding aspect of this research project is the investigation of the role of quinone cofactors in amine oxidase. As with the porhyrins, this work relies on accurate quinone model compounds for spectroscopic comparison. Crosslinking of connective tissue is carried out by copper lysil oxidase, an enzyme with a tyrosine-derived quinone at its active site. The proposed research will use Raman spectroscopy to identify the nature of quinone substituents in previously uncharacterized cofactors (as in lysil oxidase), in intermediates of the catalytic cycle, and during the biosynthesis of the cofactor.