CATALYTIC MECHANISMS OF HEME ENZYMES

本研究的目的是阐明催化 血红素加氧酶进行氧化降解的机制 铁原卟啉IX（氯化血红素）转化为铁（Fe），一氧化碳（CO）， 和胆绿素IX α。 在拟议的研究中， 中间体将通过使用化学合成的α- 羟血红素和绿血红素。的电子和分子结构 α-羟基血红素和绿血红素中间体将由 光学吸收、EPR、共振拉曼和X射线光谱。 到 为此，我们正在结合研究小组的资源和技能， 在凯斯西储大学，阿尔伯特·爱因斯坦医学院， 莱斯大学，山形大学，理研，阿贡国家实验室，还有斯坦福大学 同步辐射实验室为了有效地利用 融合蛋白质工程、卟啉合成和高级 光谱技术 在这个项目中，有几个具体问题 关于血红素加氧酶的结构、功能和机制， 被解决。 酶如何在每一步激活分子氧 三个单加氧酶循环将被确定;如何酶 当它被其产物CO束缚时，将检查其功能; 将确定抑制酶的机制; 催化机制将得到澄清。 除了井- 确定了血红素加氧酶作为血红素催化的关键酶的作用， 现在认为，这种酶的产物CO和胆绿素 作为自由基清除剂发挥重要的生理功能， 神经传递中的多功能生理信使， 血管舒张。 因此，胆绿素和CO的作用机制 其产生和控制具有极其重要的生物医学意义。

The objective of the proposed research is to elucidate the catalytic mechanism of heme oxygenase which carries out a oxidative degradation of iron protoporphyrin IX (hemin) into iron (Fe), carbon monoxide (CO), and biliverdin IXalpha. In the proposed research, the catalytic intermeditates will be prepared by using chemically synthesized alpha- hydroxyheme and verdoheme. Electronic and molecular structures of the alpha-hydroxyheme and verdoheme intermediates will be examined by optical absorption, EPR, resonance Raman, and X-ray spectroscopy. To do this, we are combining resources and skills of the research groups at Case Western Reserve Univ., Albert Einsterin College of Medicine, Rice Univ., Yamagata Univ., Riken, Argonne National Lab., and Stanford Synchrotron Radiation Lab. for an efficient utilization of the power of mergining protein engineering, porphyrin synthesis, and advanced spectroscopic techniques. In this project several specific questions concerning the structure, function and mechanisms of heme oxygenase will be addressed. How the enzyme activates molecular oxygen at each step of three mono-oxygenase cycle will be determined; how the enzyme functions when it is bound by CO, its product, will be examined; mechanisms of inhibiting the enzyme will be determined; and the catalytic mechanism will be clarified. In addition to the well- established role of heme oxygenase as a key enzyme of heme catabolism, CO and biliverdine, the products of the enzyme, are now recognized to play significant physiological functions as a free-radical scavenger and a versatile physiological messenger in neurotransmission and vasodilation, respectively. Thus, the mechanism of biliverdin and CO generation and control are of utmost biomedical importance.