Auchère Françoise, Raleiras Patrícia, Benson Linda, Venyaminov Sergei Yu, Tavares Pedro, Moura José J G, Moura Isabel, Rusnak Frank
Section of Hematology Research, Department of Biochemistry, Biomedical Mass Spectrometry Facility, Mayo Clinic, Rochester, Minnesota 55905, USA.
Inorg Chem. 2003 Feb 24;42(4):938-40. doi: 10.1021/ic0262886.
Superoxide reductases catalyze the monovalent reduction of superoxide anion to hydrogen peroxide. Spectroscopic evidence for the formation of a dinuclear cyano-bridged adduct after K(3)Fe(CN)(6) oxidation of the superoxide reductases neelaredoxin from Treponema pallidum and desulfoferrodoxin from Desulfovibrio vulgaris was reported. Oxidation with K(3)Fe(CN)(6) reveals a band in the near-IR with lambda(max) at 1020 nm, coupled with an increase of the iron content by almost 2-fold. Fourier transform infrared spectroscopy provided additional evidence with CN-stretching vibrations at 2095, 2025-2030, and 2047 cm(-)(1), assigned to a ferrocyanide adduct of the enzyme. Interestingly, the low-temperature electronic paramagnetic resonance (EPR) spectra of oxidized TpNlr reveal at least three different species indicating structural heterogeneity in the coordination environment of the active site Fe ion. Given the likely 6-coordinate geometry of the active site Fe(3+) ion in the ferrocyanide adduct, we propose that the rhombic EPR species can serve as a model of a hexacoordinate form of the active site.
超氧化物还原酶催化超氧阴离子单价还原为过氧化氢。有报道称，梅毒螺旋体的超氧化物还原酶尼尔拉毒素和普通脱硫弧菌的脱硫铁氧还蛋白在被铁氰化钾（K(3)Fe(CN)(6)）氧化后，形成了双核氰基桥联加合物的光谱证据。用铁氰化钾氧化会在近红外区域出现一个最大波长（lambda(max)）为1020 nm的吸收带，同时铁含量增加近2倍。傅里叶变换红外光谱提供了额外证据，在2095、2025 - 2030和2047 cm(-)(1)处有氰基伸缩振动，这被归因于该酶的亚铁氰化物加合物。有趣的是，氧化后的梅毒螺旋体尼尔拉毒素（TpNlr）的低温电子顺磁共振（EPR）光谱显示至少有三种不同的物种，表明活性位点铁离子的配位环境存在结构异质性。鉴于亚铁氰化物加合物中活性位点Fe(3+)离子可能的六配位几何结构，我们提出菱形EPR物种可作为活性位点六配位形式的模型。
