Capture and characterization of a reactive haem-carbenoid complex in an artificial metalloenzyme
Capture and characterization of a reactive haem-carbenoid complex in an artificial metalloenzyme
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DOI：
10.1038/s41929-018-0105-6
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发表时间：
2018-08-01
期刊：
影响因子：
37.8
通讯作者：
Hilvert, Donald
中科院分区：
文献类型：
--
作者：
Hayashi, Takahiro;Tinzl, Matthias;Hilvert, Donald
非正则氨基酸配体可用于微调金属酶的催化性能。在这里，我们展示了重组替换肌红蛋白中血红素近端的组氨酸配体N-增量-甲基组氨酸增强了蛋白质的杂乱的卡宾转移化学，使得即使在好氧条件下也能够在没有还原剂的情况下有效地进行苯乙烯环丙烷化反应。修饰的Fe(III)中心的亲电性增加，结合活性中心的微妙结构调整，允许重氮乙酸乙酯直接攻击生成活性类卡宾加合物，X-射线晶体分析表明，该加合物具有不寻常的桥联Fe(III)-C-N(吡咯)构型。量子化学计算表明，桥联络合物与更具活性的末端异构体保持平衡，确保了有效的环丙烷化反应。这些发现强调了非正则配体通过开辟新的反应途径和促进表征本来不会积累的活性物种来扩展金属酶能力的潜力。
Non-canonical amino acid ligands are useful for fine-tuning the catalytic properties of metalloenzymes. Here, we show that recombinant replacement of the histidine ligand proximal to haem in myoglobin with N-delta-methylhistidine enhances the protein's promiscuous carbene-transfer chemistry, enabling efficient styrene cyclopropanation in the absence of reductant, even under aerobic conditions. The increased electrophilicity of the modified Fe(III) centre, combined with subtle structural adjustments at the active site, allows direct attack of ethyl diazoacetate to produce a reactive carbenoid adduct, which has an unusual bridging Fe(III)-C-N(pyrrole) configuration as shown by X-ray crystallography. Quantum chemical calculations suggest that the bridged complex equilibrates with the more reactive end-on isomer, ensuring efficient cyclopropanation. These findings underscore the potential of non-canonical ligands for extending the capabilities of metalloenzymes by opening up new reaction pathways and facilitating the characterization of reactive species that would not otherwise accumulate.