An iron hydroxide moiety in the 1.35 Å resolution structure of hydrogen peroxide derived myoglobin compound II at pH 5.2
An iron hydroxide moiety in the 1.35 Å resolution structure of hydrogen peroxide derived myoglobin compound II at pH 5.2
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DOI：
10.1007/s007750100296
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发表时间：
2002-03-01
影响因子：
3
通讯作者：
Andersson, KK
中科院分区：
文献类型：
--
作者：
Hersleth, HP;Dalhus, B;Andersson, KK
O-2和过氧化物到水的生物转化以及氧原子到有机小分子的某些转化可以被不同簇或辅因子中的金属离子催化。这些反应的催化循环通过类似的金属基络合物，其中一个氧或过氧化物衍生的氧原子与催化金属中心的氧化形式配位。在基于血红素的过氧化物酶或加氧酶中，铁基（（FeO）-O-IV）形式在化合物I和化合物II中是重要的，其比铁（Fe-III）形式高二和一个氧化当量。分别在这项研究中，我们报告了1.35埃结构的化合物II模型蛋白质。通过过氧化氢与铁肌红蛋白在pH 5.2下反应而获得。与铁形式相比，分子几何形状几乎没有变化，这表明这些活性中间体不会发生大的结构变化。它进一步表明，在低pH值的主要化合物II的共振形式是羟基自由基三价铁，而不是氧代-ferryl形式，基于短氢键的远端组氨酸（2.70埃）和Fe…O距离。1.92 Angstrom Fe. O距离与辣根过氧化物酶中化合物II的EXAFS研究一致。
The biological conversions of O-2 and peroxides to water as well as certain incorporations of oxygen atoms into small organic molecules can be catalyzed by metal ions in different clusters or cofactors. The catalytic cycle of these reactions passes through similar metal-based complexes in which one oxygen- or peroxide-derived oxygen atom is coordinated to an oxidized form of the catalytic metal center. In haem-based peroxidases or oxygenases the ferryl ((FeO)-O-IV) form is important in compound I and compound II, which are two and one oxidation equivalents higher than the ferric (Fe-III) form. respectively. In this study we report the 1.35 Angstrom structure of a compound II model protein. obtained by reacting hydrogen peroxide with ferric myoglobin at pH 5.2. The molecular geometry is virtually unchanged compared to the ferric form, indicating that these reactive intermediates do not undergo large structural changes. It is further suggested that at low pH the dominating compound II resonance form is a hydroxyl radical ferric iron rather than an oxo-ferryl form, based on the short hydrogen bonding to the distal histidine (2.70 Angstrom) and the Fe...O distance. The 1.92 Angstrom Fe...O distance is in agreement with an EXAFS study of compound II in horseradish peroxidase.