Mechanism of Taurine: Alpha-Ketoglutarate Dioxygenase

Monoclonal非血红素铁（MNH-Fe）酶激活O2用于一系列令人惊叹的生物医学， 农业上和环境上重要的氧化反应。我们过去十年的工作， (in部分）通过这一授权，建立了铁（IV）-氧代（铁酰基）配合物在反应中的中间体 七种不同的MNH-Fe酶。这些复合物中的五种通过以下方式产生底物自由基： 从未活化的脂肪碳中提取氢（H <$），引发新的C-O，C- Cl/Br和C-S键。我们最近成功地将不同的结果合理化， 由<$-酮戊二酸（<$KG）依赖性脂肪族羟化酶中的（卤代）铁基复合物介导 和卤化酶，我们现在的目标是了解更复杂的铁介导的转化， 包括由以下酶显示的那些：（1）羟丙基磷酸环氧酶（HppE），其 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）碳青霉烯合酶（CarC）， 使用一个或多个酪氨酰基自由基与假定的铁酰基复合物协同作用， 手性碳的立体转化和C-C键的去饱和，从手性碳中除去两个原子， 立体中心，据报道，在一个单一的O2激活事件，以产生一个重要的一类的核心， 抗生素;和（3）2-羟乙基膦酸（2-HEP）双加氧酶（HEPD）和甲基膦酸酯 合成酶（MPnS），一对相关的酶，其使用铁基复合物来切割2-氨基-3-甲基-4-（2-氨基-3-甲基-4-氧代）-3-甲基-4-氧代- HEP在不同的4-e-氧化反应中，产生除草剂膦丝菌素的前体 （HEPD）和海洋甲烷（MPnS）的主要储存。肌醇加氧酶的研究进展 和异青霉素N合酶证明了酶的O2和C- H活化，涉及H ²提取FeIII-超氧配合物。该歧管避免了 对还原性共底物的要求（例如，KG），使四电子（4-e-）氧化。HEPD 和MPnS也可能在其铁基中间体的途径上使用这种歧管， 我们将在这里测试的假设。我们将阐明这些迷人的酶的机制， 发展其复杂的氧化化学的综合理解。

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.