Ascorbate Peroxidase Compound II Is an Iron(IV) Oxo Species,Journal of the American Chemical Society

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Ascorbate Peroxidase Compound II Is an Iron(IV) Oxo Species
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-11-10 , DOI: 10.1021/jacs.0c09108
Aaron P Ledray ₁ , Courtney M Krest ₂ , Timothy H Yosca _{1,

3} , Kaustuv Mittra _{1,

3} , Michael T Green _{1,

3}

Affiliation

The protonation state of the iron(IV) oxo (or ferryl) form of ascorbate peroxidase compound II (APX-II) is a subject of debate. It has been reported that this intermediate is best described as an iron(IV) hydroxide species. Neutron diffraction data obtained from putative APX-II crystals indicate a protonated oxygenic ligand at 1.88 Å from the heme iron. This finding, if correct, would be unprecedented. A basic iron(IV) oxo species has yet to be spectroscopically observed in a histidine-ligated heme enzyme. The importance of ferryl basicity lies in its connection to our fundamental understanding of C-H bond activation. Basic ferryl species have been proposed to facilitate the oxidation of inert C-H bonds, reactions that are unknown for histidine-ligated hemes enzymes. To provide further insight into the protonation status of APX-II, we examined the intermediate using a combination of Mössbauer and X-ray absorption spectroscopies. Our data indicate that APX-II is an iron(IV) oxo species with an Fe-O bond distance of 1.68 Å, a K-edge pre-edge absorption of 18 units, and Mössbauer parameters of ΔEq = 1.65 mm/s and δ = 0.03 mm/s.

中文翻译：

抗坏血酸过氧化物酶化合物 II 是一种铁 (IV) 氧化物种

抗坏血酸过氧化物酶化合物 II (APX-II) 的铁 (IV) 氧代（或 Ferer1）形式的质子化状态是一个有争议的话题。据报道，这种中间体最好被描述为氢氧化铁（IV）物质。从推定的 APX-II 晶体获得的中子衍射数据表明，在距离血红素铁 1.88 Å 处存在质子化含氧配体。这一发现如果正确的话，将是史无前例的。尚未在组氨酸连接的血红素酶中通过光谱观察到碱性铁 (IV) 氧代物种。 Ferry1 碱性的重要性在于它与我们对 CH 键活化的基本理解有关。碱性ferri1物种已被提议促进惰性CH键的氧化，这是组氨酸连接血红素酶未知的反应。为了进一步了解 APX-II 的质子化状态，我们结合穆斯堡尔谱和 X 射线吸收光谱检查了中间体。我们的数据表明，APX-II 是一种铁 (IV) 氧物种，Fe-O 键距为 1.68 Å，K 边前边吸收为 18 个单位，穆斯堡尔参数为 ΔEq = 1.65 mm/s 和 δ = 0.03 毫米/秒。

更新日期：2020-11-10

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