Paradigm Shift for Radical S-Adenosyl-l-methionine Reactions: The Organometallic Intermediate Ω Is Central to Catalysis.
Paradigm Shift for Radical S-Adenosyl-l-methionine Reactions: The Organometallic Intermediate Ω Is Central to Catalysis.
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DOI：
10.1021/jacs.8b04061
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发表时间：
2018-07-18
影响因子：
15
通讯作者：
Broderick JB
中科院分区：
文献类型：
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作者：
Byer AS;Yang H;McDaniel EC;Kathiresan V;Impano S;Pagnier A;Watts H;Denler C;Vagstad AL;Piel J;Duschene KS;Shepard EM;Shields TP;Scott LG;Lilla EA;Yokoyama K;Broderick WE;Hoffman BM;Broderick JB
自由基 S-腺苷-L-甲硫氨酸 (SAM) 酶包含一个庞大的超家族，通过均裂 SAM 裂解释放高反应性 5'-脱氧腺苷自由基 (5'-dAdo·)，催化所有生命必需的多种反应。因此，我们最近观察到在自由基 SAM (RS) 丙酮酸甲酸裂解酶激活酶 (PFL-AE) 反应过程中形成的具有催化能力的有机金属中间体 Ω 是相当令人惊讶的，并引发了其在超家族中广泛相关性的问题。我们现在表明，PFL-AE 中的 Ω 在各种混合顺序条件下形成中间体，表明它是该酶催化的核心。我们进一步证明，Ω 在一组 RS 酶中形成，这些 RS 酶被选择跨越整个超家族反应类型，这表明 Ω 在整个 RS 超家族的催化作用中至关重要。最后，EPR 和电子核双共振光谱证实 Ω 涉及 5′-dAdo· 和 [4Fe-4S] 簇之间的 Fe-C5′ 键。在众所周知的腺苷钴胺素（辅酶 B12）辅因子中发现了类似的有机金属键，该辅因子用于通过 5'-dAdo· 中间体引发自由基反应。因此，Ω 和辅酶 B12 通过金属-碳键均裂释放反应性 5'-dAdo· 中间体似乎是相似的。然而，辅酶 B12 参与的酶仅催化少量 (∼12) 个不同的反应，而 RS 超家族迄今为止已表征了超过 100000 个不同的序列和超过 80 种反应类型。因此，Ω 在 RS 超家族中的出现极大地扩大了自然界生物有机金属化学的范围。
Radical S-adenosyl-l-methionine (SAM) enzymes comprise a vast superfamily catalyzing diverse reactions essential to all life through homolytic SAM cleavage to liberate the highly reactive 5′-deoxyadenosyl radical (5′-dAdo·). Our recent observation of a catalytically competent organometallic intermediate Ω that forms during reaction of the radical SAM (RS) enzyme pyruvate formate-lyase activating-enzyme (PFL-AE) was therefore quite surprising, and led to the question of its broad relevance in the superfamily. We now show that Ω in PFL-AE forms as an intermediate under a variety of mixing order conditions, suggesting it is central to catalysis in this enzyme. We further demonstrate that Ω forms in a suite of RS enzymes chosen to span the totality of superfamily reaction types, implicating Ω as essential in catalysis across the RS superfamily. Finally, EPR and electron nuclear double resonance spectroscopy establish that Ω involves an Fe–C5′ bond between 5′-dAdo· and the [4Fe–4S] cluster. An analogous organometallic bond is found in the well-known adenosylcobalamin (coenzyme B12) cofactor used to initiate radical reactions via a 5′-dAdo· intermediate. Liberation of a reactive 5′-dAdo· intermediate via homolytic metal–carbon bond cleavage thus appears to be similar for Ω and coenzyme B12. However, coenzyme B12 is involved in enzymes catalyzing only a small number (∼12) of distinct reactions, whereas the RS superfamily has more than 100 000 distinct sequences and over 80 reaction types characterized to date. The appearance of Ω across the RS superfamily therefore dramatically enlarges the sphere of bio-organometallic chemistry in Nature.
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影响因子：
16.6
作者：
Driesener, Rebecca C.;Challand, Martin R.;Roach, Peter L.
通讯作者：
Roach, Peter L.
影响因子：
4.8
作者：
Peng, Yi;Veneziano, Susan E.;Broderick, Joan B.
通讯作者：
Broderick, Joan B.
DOI：
10.1073/pnas.81.5.1332
发表时间：
1984-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
--
作者：
KNAPPE, J;NEUGEBAUER, FA;GANZLER, M
通讯作者：
GANZLER, M
影响因子：
16.6
作者：
Morinaka, Brandon I.;Vagstad, Anna L.;Piel, Joern
通讯作者：
Piel, Joern
影响因子：
15
作者：
Shepard, Eric M.;Duffus, Benjamin R.;Broderick, Joan B.
通讯作者：
Broderick, Joan B.