Heme P460: A (Cross) Link to Nitric Oxide.
Heme P460: A (Cross) Link to Nitric Oxide.
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血红素P460：A（交叉）链接到一氧化氮。
DOI：
10.1021/acs.accounts.0c00573
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发表时间：
2020-12-15
影响因子：
18.3
通讯作者：
Lancaster KM
中科院分区：
文献类型：
--
作者：
Coleman RE;Lancaster KM
氨氧化细菌（AOB）将氨（NH3）转化为亚硝酸盐（NO2-）作为其主要代谢产物，从而为将NH3用作化学燃料提供了蓝图。第一个能量产生步骤涉及同源三聚体酶羟胺氧化还原酶（HAO），最初报道将羟胺（NH 2 OH）氧化为NO2-。HAO使用血红素P460辅因子作为催化位点。这个血红素由每个单体中的其他七个血红素支持，这些血红素介导电子转移。血红素P460辅因子是基于c-血红素的辅因子，其在肽骨架和卟啉大环之间具有非典型蛋白质交联。在HAO和细胞色素（cyt）P460蛋白家族中都观察到了这种辅因子。然而，存在差异;具体而言，HAO使用单个酪氨酸（Tyr）残基形成与大环的两个共价连接，而cyt P460使用赖氨酸（Lys）残基形成一个。在同时表达HAO和cyt P460的欧洲亚硝化单胞菌中，这些酶实现了NH 2 OH的氧化，并且最初都被报道产生NO2-。每一种都可以激发实现化学能受控释放的方法。光谱研究的P460辅因子的HAO是复杂的21个非P460血红素辅因子，掩盖了活性位点。然而，单血红素细胞色素P460在生物化学和光谱学上更容易接近。因此，我们使用细胞色素P460来研究生物NH 2 OH氧化。在有氧条件下，观察到亚化学计量的NO 2-的产生沿着一氧化二氮（N2 O）的产生。在厌氧条件下，N2 O是NH 2 OH氧化的唯一产物。我们已经深入了解这种酶的机制，并已表明，一个关键的中间体是铁亚硝酰基，可以解离结合的一氧化氮（NO）分子和O2反应，从而产生NO2-非生物。由于N2 O是一种含有P460辅因子的酶的真实产物，这促使我们重新研究NO2-是否是由HAO催化酶促产生的。像细胞色素P460，我们表明，HAO不产生NO2-酶，但不像细胞色素P460，其最终产物是NO，建立它作为硝化的中间体。更广泛地说，NO可以被认为是参与氮“脱固定”的所有生物体的初级代谢所共有的分子。深入研究细胞色素P460产生了广泛适用于控制生化氧化还原过程的见解。对来自亚硝化单胞菌AL 212的失活细胞色素P460的研究表明，该酶不能氧化NH 2 OH，因为它在其次级配位球中缺乏活性N中存在的谷氨酸残基。europaea cyt P460变体。恢复Glu残基的活性，揭示了第二个球基是自然界控制NH 2 OH氧化的关键。生物无机化学的一个关键教训是加强：多肽基质是决定功能的重要组成部分。我们的工作还揭示了一些关键的功能贡献的非典型血红素蛋白质交联。细胞色素P460的血红素-赖氨酸交联加强了辅因子和次级球残基的相对位置。此外，交联防止了轴向组氨酸残基的损失，这停止了催化，强调了这种独特的翻译后修饰的重要性。
Ammonia-oxidizing bacteria (AOB) convert ammonia (NH3) to nitrite (NO2–) as their primary metabolism, and thus provide a blueprint for the use of NH3 as a chemical fuel. The first energy-producing step involves the homotrimeric enzyme hydroxylamine oxidoreductase (HAO), which was originally reported to oxidize hydroxylamine (NH2OH) to NO2–. HAO uses the heme P460 cofactor as the site of catalysis. This heme is supported by seven other c hemes in each monomer that mediate electron transfer. Heme P460 cofactors are c-heme-based cofactors that have atypical protein cross-links between the peptide backbone and the porphyrin macrocycle. This cofactor has been observed in both the HAO and cytochrome (cyt) P460 protein families. However, there are differences; specifically, HAO uses a single tyrosine (Tyr) residue to form two covalent attachments to the macrocycle whereas cyt P460 uses a lysine (Lys) residue to form one. In Nitrosomonas europaea, which expresses both HAO and cyt P460, these enzymes achieve the oxidation of NH2OH and were both originally reported to produce NO2–. Each can inspire means to effect controlled release of chemical energy. Spectroscopically studying the P460 cofactors of HAO is complicated by the 21 non-P460 heme cofactors which obscure the active site. However, mono-heme cyt P460 is more approachable biochemically and spectroscopically. Thus, we have used cyt P460 to study biological NH2OH oxidation. In aerobic conditions, substoichiometric production of NO2– was observed along with production of nitrous oxide (N2O). Under anaerobic conditions, however, N2O was the exclusive product of NH2OH oxidation. We have advanced understanding of the mechanism of this enzyme and have showed that a key intermediate is a ferric nitrosyl that can dissociate the bound nitric oxide (NO) molecule and react with O2, thus producing NO2– abiotically. Because N2O was the true product of one P460 cofactor-containing enzyme, this prompted us to reinvestigate whether NO2– is enzymatically generated from HAO catalysis. Like cyt P460, we showed that HAO does not produce NO2– enzymatically, but unlike cyt P460, its final product is NO, establishing it as an intermediate of nitrification. More broadly, NO can be recognized as molecule common to the primary metabolisms of all organisms involved in nitrogen “defixation.” Delving deeper into cyt P460 yielded insights broadly applicable to controlled biochemical redox processes. Studies of an inactive cyt P460 from Nitrosomonas sp. AL212 showed that this enzyme was unable to oxidize NH2OH because it lacked a glutamate residue in its secondary coordination sphere that was present in the active N. europaea cyt P460 variant. Restoring the Glu residue imbued activity, revealing that a second-sphere base is Nature’s key to controlled oxidation of NH2OH. A key lesson of bioinorganic chemistry is reinforced: the polypeptide matrix is an essential part of dictating function. Our work also exposed some key functional contributions of non-canonical heme-protein cross-links. The heme-Lys cross-link of cyt P460 enforces the relative position of the cofactor and secondary-sphere residues. Moreover, the cross-link prevents the loss of the axial histidine residue, which stops catalysis, emphasizing the importance of this unique post-translational modification.
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影响因子：
4.1
作者：
ANDERSON, JH
通讯作者：
ANDERSON, JH
DOI：
10.1107/s1744309109046119
发表时间：
2009-12-01
影响因子：
0.9
作者：
Cedervall, Peder E.;Hooper, Alan B.;Wilmot, Carrie M.
通讯作者：
Wilmot, Carrie M.
DOI：
10.1016/0005-2744(79)90220-1
发表时间：
1979-01-01
期刊：
BIOCHIMICA ET BIOPHYSICA ACTA
影响因子：
--
作者：
HOOPER, AB;TERRY, KR
通讯作者：
TERRY, KR
DOI：
10.1021/je030121p
发表时间：
2003-09-01
期刊：
JOURNAL OF CHEMICAL AND ENGINEERING DATA
影响因子：
--
作者：
Cisneros, LO;Rogers, WJ;Koseki, H
通讯作者：
Koseki, H
DOI：
10.1073/pnas.1704504114
发表时间：
2017-08-01
影响因子：
11.1
作者：
Caranto, Jonathan D.;Lancaster, Kyle M.
通讯作者：
Lancaster, Kyle M.