Spectroscopic characterization and ligand-binding properties of chlorite dismutase from the chlorate respiring bacterial strain GR-1
Spectroscopic characterization and ligand-binding properties of chlorite dismutase from the chlorate respiring bacterial strain GR-1
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DOI：
10.1046/j.1432-1033.2002.03208.x
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发表时间：
2002-10-01
期刊：
影响因子：
--
通讯作者：
Hagen, WR
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文献类型：
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作者：
Hagedoorn, PL;de Geus, DC;Hagen, WR
亚氯酸盐歧化酶（EC 1.13.11.49），一种能够将亚氯酸盐还原为氯化物同时产生分子氧的酶，已经使用EPR和光学光谱进行了表征。GR-1 α-歧化酶的EPR谱显示了两种不同的高自旋铁血红素种类，我们将其命名为“窄”（g（x，y，z）= 6.24，5.42，2.00）和“宽”（g（z，y，x）= 6.70，5.02，2.00）。光谱证据提出了一个近端组氨酸协调血红素铁中心的酶。亚铁酶的UV/可见光谱和氢氧化铁和咪唑加合物的EPR光谱是血红素蛋白与轴向组氨酸协调铁的特征。此外，已发现底物类似物亚硝酸盐和过氧化氢与铁歧化酶结合。过氧化氢加合物的EPR光谱显示高自旋和低自旋铁信号的损失和尖锐的自由基信号的出现。亚铁酶的NO加合物表现出典型的五配位血红素铁亚硝酰加合物的低自旋EPR信号。近端组氨酸和铁之间的键似乎很弱，可以在NO结合时断裂。组氨酸歧化酶的中点电位E-m（Fe 3 +/2+）= -23 mV，高于大多数血红素酶。的光谱特征和氧化还原性质的SOD更类似于气敏血红素蛋白，如鸟苷酸环化酶和球蛋白，而不是血红素酶。
Chlorite dismutase (EC 1.13.11.49), an enzyme capable of reducing chlorite to chloride while producing molecular oxygen, has been characterized using EPR and optical spectroscopy. The EPR spectrum of GR-1 chlorite dismutase shows two different high-spin ferric heme species, which we have designated 'narrow' (g(x,y,z) = 6.24, 5.42, 2.00) and 'broad' (g(z,y,x) = 6.70, 5.02, 2.00). Spectroscopic evidence is presented for a proximal histidine co-ordinating the heme iron center of the enzyme. The UV/visible spectrum of the ferrous enzyme and EPR spectra of the ferric hydroxide and imidazole adducts are characteristic of a heme protein with an axial histidine co-ordinating the iron. Furthermore, the substrate analogs nitrite and hydrogen peroxide have been found to bind to ferric chlorite dismutase. EPR spectroscopy of the hydrogen peroxide adduct shows the loss of both high-spin and low-spin ferric signals and the appearance of a sharp radical signal. The NO adduct of the ferrous enzyme exhibits a low-spin EPR signal typical of a five-co-ordinate heme iron nitrosyl adduct. It seems that the bond between the proximal histidine and the iron is weak and can be broken upon binding of NO. The midpoint potential, E-m(Fe3+/2+ ) = -23 mV, of chlorite dismutase is higher than for most heme enzymes. The spectroscopic features and redox properties of chlorite dismutase are more similar to the gas-sensing hemoproteins, such as guanylate cyclase and the globins, than to the heme enzymes.