Two Distinct Mechanisms for C-C Desaturation by Iron(II)- and 2-(Oxo)glutarate-Dependent Oxygenases: Importance of α-Heteroatom Assistance.
Two Distinct Mechanisms for C-C Desaturation by Iron(II)- and 2-(Oxo)glutarate-Dependent Oxygenases: Importance of α-Heteroatom Assistance.
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DOI：
10.1021/jacs.8b01933
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发表时间：
2018-06-13
影响因子：
15
通讯作者：
Bollinger JM Jr
中科院分区：
文献类型：
--
作者：
Dunham NP;Chang WC;Mitchell AJ;Martinie RJ;Zhang B;Bergman JA;Rajakovich LJ;Wang B;Silakov A;Krebs C;Boal AK;Bollinger JM Jr
通过非血红素Fe（IV）-氧代（铁基）络合物的脂肪族碳的羟基化通过氢原子（H·）转移（HAT）到铁基和随后的碳自由基与Fe（III）配位的氧之间的偶联（称为反弹）进行。使用H·-提取铁基复合物进行其他转化的酶必须抑制反弹或进一步处理羟基化中间体。对于烯烃安装C-C去饱和，已经提出从碳α到自由基的Fe（III）-OH络合物的第二HAT抢占反弹。第二个位点的氘（2 H）应该会减慢这一步，可能会使反弹具有竞争力。由两种相关的L-精氨酸修饰铁（II）和2-（氧代）戊二酸依赖性（Fe/2 OG）加氧酶介导的去饱和在这个关键测试中表现相反，涉及不同的机制。NapI是来自萘啶霉素生物合成途径的L-Arg 4，5-去饱和酶，它首先从C5中提取H·，但无论C4含有1H还是2 H，都会将该位点羟基化（导致胍释放）到相同的适度程度。相比之下，当C3（第二氢供体）含有2 H时，VioC（来自紫霉素生物合成途径的L-Arg 3-羟化酶）对L-高精氨酸（L-hArg）的意想不到的3，4-去饱和相对于C4羟基化明显不利。通过N6的嵌合辅助允许在NapI反应中除去作为质子的C4-H，但是，在VioC去饱和中不可能有这样的辅助，需要第二个HAT步骤（来自C3）。在含有钒基铁基模拟物的VioC的X射线晶体结构中，两个L-hArg碳与氧配体的紧密接近（≤ 3.5 μ π ι）支持并合理化了顺序HAT机制。结果表明，尽管顺序HAT机制是可行的，但其几何要求可能使竞争羟基化不可避免，从而解释了Fe/2 OG去饱和酶的几乎所有天然底物中α-杂原子的存在。
Hydroxylation of aliphatic carbons by non-heme Fe(IV)-oxo (ferryl) complexes proceeds by hydrogen-atom (H•) transfer (HAT) to the ferryl and subsequent coupling between the carbon radical and Fe(III)-coordinated oxygen (termed rebound). Enzymes that use H•-abstracting ferryl complexes for other transformations must either suppress rebound or further process hydroxylated intermediates. For olefin-installing C–C desaturations, it has been proposed that a second HAT to the Fe(III)–OH complex from the carbon α to the radical preempts rebound. Deuterium (2H) at the second site should slow this step, potentially making rebound competitive. Desaturations mediated by two related L-arginine-modifying iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases behave oppositely in this key test, implicating different mechanisms. NapI, the L-Arg 4,5-desaturase from the naphthyridinomycin biosynthetic pathway, abstracts H• first from C5 but hydroxylates this site (leading to guanidine release) to the same modest extent whether C4 harbors 1H or 2H. By contrast, an unexpected 3,4-desaturation of L-homoarginine (L-hArg) by VioC, the L-Arg 3-hydroxylase from the viomycin biosynthetic pathway, is markedly disfavored relative to C4 hydroxylation when C3 (the second hydrogen donor) harbors 2H. Anchimeric assistance by N6 permits removal of the C4-H as a proton in the NapI reaction, but, with no such assistance possible in the VioC desaturation, a second HAT step (from C3) is required. The close proximity (≤ 3.5 Å) of both L-hArg carbons to the oxygen ligand in an x-ray crystal structure of VioC harboring a vanadium-based ferryl mimic supports and rationalizes the sequential-HAT mechanism. The results suggest that, although the sequential-HAT mechanism is feasible, its geometric requirements may make competing hydroxylation unavoidable, thus explaining the presence of α-heteroatoms in nearly all native substrates for Fe/2OG desaturases.
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DOI：
10.1021/jp404743d
发表时间：
2013-09-12
期刊：
The journal of physical chemistry. B
影响因子：
--
作者：
Casey TM;Grzyska PK;Hausinger RP;McCracken J
通讯作者：
McCracken J
DOI：
10.1111/j.1742-4658.2009.07085.x
发表时间：
2009-07
期刊：
The FEBS journal
影响因子：
--
作者：
Helmetag V;Samel SA;Thomas MG;Marahiel MA;Essen LO
通讯作者：
Essen LO
影响因子：
3
作者：
GROVES, JT
通讯作者：
GROVES, JT
影响因子：
16.6
作者：
Braeuer, Alois;Beck, Philipp;Groll, Michael
通讯作者：
Groll, Michael
影响因子：
--
作者：
Hiratsuka, Tomoshige;Koketsu, Kento;Oikawa, Hideaki
通讯作者：
Oikawa, Hideaki