An Iron(IV)-Oxo Intermediate Initiating l-Arginine Oxidation but Not Ethylene Production by the 2-Oxoglutarate-Dependent Oxygenase, Ethylene-Forming Enzyme.
An Iron(IV)-Oxo Intermediate Initiating l-Arginine Oxidation but Not Ethylene Production by the 2-Oxoglutarate-Dependent Oxygenase, Ethylene-Forming Enzyme.
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DOI：
10.1021/jacs.0c10923
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发表时间：
2021-02-10
影响因子：
15
通讯作者：
Bollinger JM Jr
中科院分区：
文献类型：
--
作者：
Copeland RA;Davis KM;Shoda TKC;Blaesi EJ;Boal AK;Krebs C;Bollinger JM Jr
乙烯形成酶（EFE）是一种双功能铁（II）和2-酮戊二酸依赖性（Fe/2 OG）加氧酶。在其主要（EF）反应中，它将2 OG的碳1，2和5转化为CO2，碳3和4转化为乙烯，这是一种四电子氧化，与所有其他Fe/2 OG酶介导的2 OG到琥珀酸的简单脱羧反应截然不同。EFE还催化一个次要反应，其中正常的脱羧作用与L-精氨酸（EF途径所需的活化剂）的氧化偶联，导致其转化为L-谷氨酸半醛和胍。在这里，我们表明，与先例一致，L-Arg-氧化（RO）途径通过铁（IV）-氧代（ferryl）中间体进行。使用5，5-[2 H2]-L-Arg使铁基复合物的衰变减慢>16倍，这意味着RO是由来自C5的氢原子转移（HAT）引发的。这种大底物氘动力学同位素效应对EF：RO分配比没有影响意味着相同的铁基中间体不能在EF途径上;途径必须更早地分叉。与这一结论一致，带有Asp 191 Glu配体取代的变体酶积累的铁基复合物约为野生型酶的四倍，并且EF：RO分配比降低约40倍。这种几乎保守的取代EF途径的选择性损害意味着它具有异常严格的立体电子要求。一个活性位点，类似的电荷胍对，其中涉及的L-Arg底物/激活剂，是独特的EFE在四个晶体学特征的L-Arg修饰的Fe/2 OG加氧酶，可以用来选择性地稳定过渡态，导致独特的EF分支。
Ethylene-forming enzyme (EFE) is an ambifunctional iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenase. In its major (EF) reaction, it converts carbons 1, 2, and 5 of 2OG to CO2 and carbons 3 and 4 to ethylene, a four-electron oxidation drastically different from the simpler decarboxylation of 2OG to succinate mediated by all other Fe/2OG enzymes. EFE also catalyzes a minor reaction, in which the normal decarboxylation is coupled to oxidation of L-arginine (a required activator for the EF pathway), resulting in its conversion to L-glutamate semialdehyde and guanidine. Here we show that, consistent with precedent, the L-Arg-oxidation (RO) pathway proceeds via an iron(IV)-oxo (ferryl) intermediate. Use of 5,5-[2H2]-L-Arg slows decay of the ferryl complex by >16-fold, implying that RO is initiated by hydrogen-atom transfer (HAT) from C5. That this large substrate deuterium kinetic isotope effect has no impact on the EF:RO partition ratio implies that the same ferryl intermediate cannot be on the EF pathway; the pathways must diverge earlier. Consistent with this conclusion, the variant enzyme bearing the Asp191Glu ligand substitution accumulates ~ four times as much of the ferryl complex as the wild-type enzyme and exhibits a ~ 40-fold diminished EF:RO partition ratio. The selective detriment of this nearly conservative substitution to the EF pathway implies that it has unusually stringent stereoelectronic requirements. An active-site, like-charge guanidium pair, which involves the L-Arg substrate/activator and is unique to EFE among four crystallographically characterized L-Arg-modifying Fe/2OG oxygenases, may serve to selectively stabilize the transition state leading to the unique EF branch.
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影响因子：
15
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
通讯作者：
Bollinger JM Jr
影响因子：
3.9
作者：
Hangasky, John A.;Taabazuing, Cornelius Y.;Knapp, Michael J.
通讯作者：
Knapp, Michael 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
DOI：
10.1016/0006-291x(92)91081-z
发表时间：
1992-10-30
影响因子：
3.1
作者：
FUKUDA, H;OGAWA, T;MORINO, Y
通讯作者：
MORINO, Y
影响因子：
3.9
作者：
Grzyska, Piotr K.;Muller, Tina A.;Hausinger, Robert P.
通讯作者：
Hausinger, Robert P.