标题：Insights into the unprecedented epoxidation mechanism of fumitremorgin B endoperoxidase (FtmOx1) from Aspergillus fumigatus by QM/MM calculations
作者：Wang, Xiya; Su, Hao; Liu, Yongjun
作者机构：[Wang, Xiya; Su, Hao; Liu, Yongjun] Shandong Univ, Sch Chem & Chem Engn, Jinan 250100, Shandong, Peoples R China.
通讯作者地址：[Liu, YJ]Shandong Univ, Sch Chem & Chem Engn, Jinan 250100, Shandong, Peoples R China.
来源：PHYSICAL CHEMISTRY CHEMICAL PHYSICS
摘要：Fumitremorgin B endoperoxidase (FtmOx1) from Aspergillus fumigatus is the first reported alpha-ketoglutaratedependent mononuclear non-haem iron enzyme that catalyzes the endoperoxide formation reaction, converting Fumitremorgin B to verruculogen. Experiments reveal that the molecular oxygen (O-2) is incorporated into verruculogen without O-O bond scission, which differs from the currently known non- haem iron enzymes, but the mechanistic details are still unclear. In this paper, on the basis of the crystal structures of FtmOx1 in complex with either the co-substrate (alpha-ketoglutarate) or the substrate (fumitremorgin B), a ternary complex model of the enzyme-alpha-ketoglutarate-substrate has been constructed, and combined quantum mechanics and molecular mechanics (QM/ MM) calculations have been performed to unravel the novel mechanism of FtmOx1. Our calculations indicate the quintet of the Fe-IV=O complex as the ground state. The Fe-IV=O complex firstly abstracts a hydrogen from the hydroxyl of Tyr228 to initiate the reaction, which corresponds to a lower energy barrier (9.1 kcal mol (-1)). If the Fe-IV=O complex directly abstracts a hydrogen from C-21 of the substrate, the energy barrier would increase to 33.9 kcal mol(-1). When Tyr228 was mutated to Ala228, this energy barrier decreases to 24.0 kcal mol (-1). In the subsequent reaction, the generated Tyr228 radical abstracts the hydrogen (H-2) from C-21 of the substrate with an energy barrier of 23.8 kcal mol(-1). The second molecular oxygen binds to the C-21 radical of the substrate in the active pocket and further completes the epoxidation with an energy barrier of 4.8 kcal mol(-1). These results may provide useful information for understanding the reaction mechanism of FtmOx1 and provide guidance for further experimental investigations.