Department of Chemistry, Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA.
Nat Commun. 2012;3:1042. doi: 10.1038/ncomms2052.
The final step of the methylerythritol phosphate isoprenoid biosynthesis pathway is catalysed by the iron-sulphur enzyme IspH, producing the universal precursors of terpenes: isopentenyl diphosphate and dimethylallyl diphosphate. Here we report an unforeseen reaction discovered during the investigation of the interaction of IspH with acetylene inhibitors by X-ray crystallography, Mößbauer, and nuclear magnetic resonance spectroscopy. In addition to its role as a 2H(+)/2e(-) reductase, IspH can hydrate acetylenes to aldehydes and ketones via anti-Markovnikov/Markovnikov addition. The reactions only occur with the oxidised protein and proceed via η(1)-O-enolate intermediates. One of these is characterized crystallographically and contains a C4 ligand oxygen bound to the unique, fourth iron in the 4Fe-4S cluster: this intermediate subsequently hydrolyzes to produce an aldehyde product. This unexpected side to IspH reactivity is of interest in the context of the mechanism of action of other acetylene hydratases, as well as in the design of antiinfectives targeting IspH.
甲基赤藓醇磷酸异戊烯基转移酶途径的最后一步由铁硫酶 IspH 催化，生成萜烯的通用前体：异戊烯二磷酸和二甲基烯丙基二磷酸。在这里，我们通过 X 射线晶体学、穆斯堡尔和核磁共振波谱研究了 IspH 与乙炔抑制剂相互作用时，发现了一个意想不到的反应。除了作为 2H(+)/2e(-)还原剂的作用外，IspH 还可以通过反 Markovnikov/Markovnikov 加成将乙炔水合为醛和酮。这些反应仅在氧化蛋白存在下发生，并通过 η(1)-O-烯醇化物中间体进行。其中一个中间体通过晶体学进行了表征，其中一个 C4 配体氧与 4Fe-4S 簇中的独特的第四个铁结合：这个中间体随后水解生成醛产物。IspH 反应的这种意外的副反应在其他乙炔水合酶的作用机制以及针对 IspH 的抗感染药物设计方面具有重要意义。
