Endoperoxide formation by an α-ketoglutarate-dependent mononuclear non-haem iron enzyme.
Endoperoxide formation by an α-ketoglutarate-dependent mononuclear non-haem iron enzyme.
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DOI：
10.1038/nature15519
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发表时间：
2015-11-26
期刊：
影响因子：
64.8
通讯作者：
Zhang YJ
中科院分区：
文献类型：
--
作者：
Yan W;Song H;Song F;Guo Y;Wu CH;Her AS;Pu Y;Wang S;Naowarojna N;Weitz A;Hendrich MP;Costello CE;Zhang L;Liu P;Zhang YJ
许多含过氧的次生代谢物已被分离出来，并显示对人体健康有益。然而，大多数内过氧化物生物合成的机制尚不清楚。虽然内过氧化物在一些情况下被认为是关键的反应中间体，但唯一被充分表征的内过氧化物生物合成酶是前列腺素H合成酶，一种含血酶。来自烟曲霉的Fumitremorgin B内过氧化物酶（FtmOx1）是第一个报道的α-酮戊二酸依赖的单核非血红素铁酶，可以催化内过氧化物形成反应。为了阐明这种独特化学转变的机理细节，我们报道了FtmOx1的x射线晶体结构及其与共底物（α-酮戊二酸酯）或底物（fumitremorgin B）形成的二元配合物。独特的是，在α-酮戊二酸以双齿方式与单核铁中心结合后，剩余的供氧结合和活化的开放位点被酪氨酸残基（Y224）屏蔽，不受底物或溶剂的影响。当用丙氨酸或苯丙氨酸取代Y224时，FtmOx1的催化作用从内过氧化物形成转向更常见的羟基化。随后通过停止流动光学吸收光谱和冷冻猝灭电子顺磁共振光谱的组合表征支持FtmOx1催化过程中存在瞬态自由基。我们的研究结果有助于揭示这种内过氧化物形成反应的新机制。
Many peroxy-containing secondary metabolites have been isolated and shown to provide beneficial effects to human health. Yet, the mechanisms of most endoperoxide biosyntheses are not well understood. Although endoperoxides have been suggested as key reaction intermediates in several cases, the only well-characterized endoperoxide biosynthetic enzyme is prostaglandin H synthase, a haem-containing enzyme. Fumitremorgin B endoperoxidase (FtmOx1) from Aspergillus fumigatus is the first reported α-ketoglutarate-dependent mononuclear non-haem iron enzyme that can catalyse an endoperoxide formation reaction. To elucidate the mechanistic details for this unique chemical transformation, we report the X-ray crystal structures of FtmOx1 and the binary complexes it forms with either the co-substrate (α-ketoglutarate) or the substrate (fumitremorgin B). Uniquely, after α-ketoglutarate binding to the mononuclear iron centre in a bidentate fashion, the remaining open site for oxygen binding and activation is shielded from the substrate or the solvent by a tyrosine residue (Y224). Upon replacing Y224 with alanine or phenylalanine, the FtmOx1 catalysis diverts from endoperoxide formation to the more commonly observed hydroxylation. Subsequent characterizations by a combination of stopped-flow optical absorption spectroscopy and freeze-quench electron paramagnetic resonance spectroscopy support the presence of transient radical species in FtmOx1 catalysis. Our results help to unravel the novel mechanism for this endoperoxide formation reaction.