Bacterial nitric oxide reductase (NorBC) models employing click chemistry
Bacterial nitric oxide reductase (NorBC) models employing click chemistry
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DOI：
10.1016/j.jinorgbio.2023.112280
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发表时间：
2023-06-21
影响因子：
3.9
通讯作者：
Lehnert，Nicolai
中科院分区：
文献类型：
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作者：
Harland，Jill B.;Samanta，Subhra;Lehnert，Nicolai
细菌 NO 还原酶 (NorBC orcNOR) 是一种存在于反硝化细菌中的膜结合酶，可催化 NO 双电子还原为 N2O 和水。 NorBC 的运作机制备受争议，因为这种酶很难使用，而且迄今为止还没有鉴定出 NO 还原反应的中间体。 NorBC 独特的活性位点由 hemeb3/非血红素 FeBdiiron 中心组成。合成模型复合物提供了深入了解这种酶可能的机械替代方案的机会。在本文中，我们提出了 NorBC 的三个新合成模型系统，由点击修饰的基于 BMPA 的配体（BMPA = 双（甲基吡啶基）胺）的四苯基卟啉衍生物组成，用于模拟酶中的非血红素位点。这些配合物已通过 EPR、IR 和 UV-Vis 光谱进行了表征。然后研究了与NO的反应性，发现以BMPA-羧酸盐配体作为非血红素成分的复合物在非血红素铁位点对NO的亲和力非常低。如果羧酸盐官能团被酚盐或吡啶基团取代，则反应性恢复并观察到二铁二亚硝基络合物的形成。在亚硝基化复合物发生单电子还原后，按照 NO 还原的半还原途径，在所有三种情况下均观察到二亚硝基铁复合物 (DNIC) 的形成，但未检测到 N2O。
Bacterial NO Reductase (NorBC orcNOR) is a membrane-bound enzyme found in denitrifying bacteria that catalyzes the two-electron reduction of NO to N2O and water. The mechanism by which NorBC operates is highly debated, due to the fact that this enzyme is difficult to work with, and no intermediates of the NO reduction reaction could have been identified so far. The unique active site of NorBC consists of a hemeb3/non-heme FeBdiiron center. Synthetic model complexes provide the opportunity to obtain insight into possible mechanistic alternatives for this enzyme. In this paper, we present three new synthetic model systems for NorBC, consisting of a tetraphenylporphyrin-derivative clicked to modified BMPA-based ligands (BMPA = bis(methylpyridyl)amine) that model the non-heme site in the enzyme. These complexes have been characterized by EPR, IR and UV–Vis spectroscopy. The reactivity with NO was then investigated, and it was found that the complex with the BMPA-carboxylate ligand as the non-heme component has a very low affinity for NO at the non-heme iron site. If the carboxylate functional group is replaced with a phenolate or pyridine group, reactivity is restored and formation of a diiron dinitrosyl complex was observed. Upon one-electron reduction of the nitrosylated complexes, following the semireduced pathway for NO reduction, formation of dinitrosyl iron complexes (DNICs) was observed in all three cases, but no N2O could be detected.