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Abstract：
Understanding the reaction mechanism of enzymes at the molecular level is generally a difficult task, since many parameters affect the turnover. Often, due to high reactivity and formation of transient species or intermediates, detailed information on enzymatic catalysis is obtained by means of model substrates. Whenever possible, it is essential to confirm a reaction mechanism based on substrate analogues or model systems by using the physiological substrates. Here we disclose the ferrous iron incorporation mechanism, in solution, and in crystallo, by the coproporphyrin III-coproporphyrin ferrochelatase complex from the firmicute, pathogen, and antibiotic resistant, Listeria monocytogenes. Coproporphyrin ferrochelatase plays an important physiological role as the metalation represents the penultimate reaction step in the prokaryotic coproporphyrin-dependent heme biosynthetic pathway, yielding coproheme (ferric coproporphyrin III). By following the metal titration with resonance Raman spectroscopy and x-ray crystallography, we prove that upon metalation the saddling distortion becomes predominant both in the crystal and in solution. This is a consequence of the readjustment of hydrogen bond interactions of the propionates with the protein scaffold during the enzymatic catalysis. Once the propionates have established the interactions typical of the coproheme complex, the distortion slowly decreases, to reach the almost planar final product.
摘要：
在分子水平上了解酶的反应机理通常是一项艰巨的任务，由于许多参数影响营业额。通常,由于高反应性和瞬态物种或中间体的形成，有关酶催化的详细信息是通过模型底物获得的。只要有可能,必须通过使用生理底物来确认基于底物类似物或模型系统的反应机理。这里我们公开了亚铁掺入机理，在溶液和晶体中，由同系物中的共卟啉III-共卟啉铁螯合酶络合物，病原体和抗生素抗性，单核细胞增生李斯特菌。卟啉铁螯合酶起着重要的生理作用，因为金属化代表了原核卟啉依赖血红素生物合成途径中倒数第二个反应步骤，产生共聚血红素（铁卟啉III）。通过使用共振拉曼光谱和X射线晶体学进行金属滴定，我们证明，在金属化后，鞍形畸变在晶体和溶液中均占主导地位。这是在酶催化期间丙酸盐与蛋白质支架的氢键相互作用的重新调整的结果。一旦丙酸酯建立了共丙血红素复合物的典型相互作用，失真慢慢减少，达到几乎平面的最终产品。本文受版权保护。保留所有权利。
