Mechanism of Taurine: Alpha-Ketoglutarate Dioxygenase

单核非血红素铁(MNH-Fe)酶激活氧，在生物医学上， 在农业和环境方面具有重要意义的氧化反应。我们过去十年的工作，得到支持 (部分)通过这笔赠款，确立了铁(IV)-氧代(铁基)络合物在反应中的中间体 七种不同的MNH-Fe酶。其中五个络合物通过以下方式产生底物自由基 从未活化的脂肪族碳中提取氢(H？)，引发新的C-O，C- CL/Br键和C-S键。我们最近在使不同的结果合理化方面取得的成功鼓舞了我们 依赖酮戊二酸(KG)的脂肪族羟基酶中的(晕)铁基络合物的介导 和卤代酶，我们现在的目标是了解更复杂的铁基介导的转化， 包括这些酶表现出的：(1)羟丙基磷酸盐环氧酶(HppE)，它 催化醇的1，3-脱氢为环氧化物，使用过氧化氢作为 氧化剂，在抗生素磷霉素的生物合成中；(2)碳青霉烯类合成酶(CARC)，它 使用一个或多个酪氨酸基与推定的铁基络合物结合以促进 手性碳的立体转化和C-C键的脱饱和度 立体中心，据报道，在单个O2激活事件中，产生了一类重要的 抗生素；和(3)2-羟乙基磷酸盐(2-HEP)双加氧酶(HEPD)和甲基膦 合成酶(MPNS)是一对相关的酶，它使用铁基络合物来裂解2-甲基-4-甲氧基苯乙酸乙二酯的C-C键。 HEP在不同的4-e氧化反应中，产生除草剂草甘膦的前体 (HEPD)和一个主要的海洋甲烷储藏库(MPN)。肌醇加氧酶的研究近况 而异青霉素N合成酶对酶的O2和C-表现出根本不同的多样性。 H活化，包括H？提取FeIII-超氧配合物。这种流形避免了 需要还原的辅助底物(例如，KG)，实现四电子(4-e-)氧化。HEPD 而MPN也可能在它们的铁基中间体的路径上使用这种歧管，a 我们将在这里测试的假设。我们将阐明这些令人着迷的酶的机制 对其复杂的氧化化学有一个完整的了解。

Mononuclear non-heme-iron (MNH-Fe) enzymes activate O2 for a stunning array of biomedically, agriculturally, and environmentally important oxidation reactions. Our past decade's work, supported (in part) by this grant, established the intermediacy of iron(IV)-oxo (ferryl) complexes in the reactions of seven different MNH-Fe enzymes. Five of these complexes generate substrate radicals by abstracting hydrogen (H¿) from unactivated aliphatic carbons, initiating formation of new C-O, C- Cl/Br, and C-S bonds. Energized by our recent success in rationalizing the divergent outcomes mediated by the (halo)ferryl complexes in the ¿-ketoglutarate(¿KG)-dependent aliphatic hydroxylases and halogenases, we now aim to understand even more complex ferryl-mediated transformations, including those exhibited by the enzymes: (1) hydroxypropylphosponate epoxidase (HppE), which catalyzes the 1,3-dehydrogenation of an alcohol to an epoxide, using hydrogen peroxide as the oxidant, in the biosynthesis of the antibiotic, fosfomycin; (2) carbapenem synthase (CarC), which uses one or more tyrosyl radical in concert with the presumptive ferryl complex to promote stereoinversion of a chiral carbon and desaturation of a C-C bond two atoms removed from the stereocenter, reportedly in a single O2 activation event, to produce the core of an important class of antibiotics; and (3) 2-hydroxyethylphosponate (2-HEP) dioxygenase (HEPD) and methylphosphonate synthase (MPnS), a pair of related enzymes that use ferryl complexes to cleave the C-C bond of 2- HEP in distinct 4-e- oxidation reactions, producing a precursor to the herbicide phosphinothricin (HEPD) and a major store of oceanic methane (MPnS). Our past studies on myo-inositol oxygenase and isopenicillin N synthase demonstrated a fundamentally distinct manifold for enzymatic O2 and C- H activation, involving H¿ abstracting FeIII-superoxo complexes. This manifold obviates the requirement for a reducing co-substrate (e.g., ¿KG), enabling four-electron (4-e-) oxidations. HEPD and MPnS are likely also to employ this manifold on the pathways to their ferryl intermediates, a hypothesis that we will test here. We will elucidate the mechanisms of these fascinating enzymes to develop an integrated understanding of their complex oxidation chemistry.