THE REACTION OF HYDROGEN-PEROXIDE WITH PULSED CYTOCHROME BO FROM ESCHERICHIA-COLI
THE REACTION OF HYDROGEN-PEROXIDE WITH PULSED CYTOCHROME BO FROM ESCHERICHIA-COLI
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DOI：
10.1111/j.1432-1033.1994.tb20102.x
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发表时间：
1994-12-01
期刊：
影响因子：
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通讯作者：
RICH, PR
中科院分区：
文献类型：
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作者：
MOODY, AJ;RICH, PR
过氧化氢（H2 O2）与脉冲细胞色素bo的反应导致酶的特征光谱变化。差异光谱在401、494和628 nm处显示最小值，在420、约468、526和556 nm处显示最大值。Δ β（420）-Δ β（401）在73-86 mM（-1）的范围内。cm（-1）和Δ Δ δ（556）-Δ δ（628）为7.7-9.6 mM（-1）。cm（-1）（还原-氧化光谱的Δ λ（560）-Δ λ（580）为20.5 mM（-1））。cm（-1））。通过滴定光谱变化确定的反应的化学计量比为1：1。反应的二级速率常数为1.0- 1.5 × 10 ~（3）M ~（-1）。s（-1），在6.5-8.0的范围内与pH无关。反应产物以1- 4 × 10 ~（-4）s ~（-1）的一级速率常数衰变，因此K-d值显然在0.05-0.40 μ M范围内。喹啉诱导的营业额后立即观察到的光谱变化，或在稳态营业额诱导肼或一氧化碳，是定性相同的H2 O2诱导虽然较低的振幅。H2 O2的加入通过增加光谱变化的幅度来扰乱肼诱导或CO诱导的稳态，但没有质的变化。从这一观察结果和1：1的化学计量反应，我们得出结论，由H2 O2诱导的中间体，我们称之为F-，只需要从外部来源向酶提供两个电子。
The reaction of hydrogen peroxide (H2O2) with pulsed cytochrome bo leads to characteristic spectral changes in the enzyme. The difference spectrum shows minima at 401, 494 and 628 nm, and maxima at 420, approximately 468, 526 and 556 nm. Delta epsilon(420)-epsilon(401) is in the range 73-86 mM(-1) . cm(-1) and Delta epsilon(556)-epsilon(628) is 7.7-9.6 mM(-1) . cm(-1) (taking Delta epsilon(560)-epsilon(580) for the reduced minus oxidised spectrum to be 20.5 mM(-1) . cm(-1)). The stoichiometry of the reaction, determined by titration of the spectral changes, is 1:1. The second order rate constant for the reaction, which is 1.0-1.5X10(3) M(-1) . s(-1) at 20 degrees C, is independent of pH over the range 6.5-8.0. The product of the reaction decays with a first-order rate constant in the range 1-4X10(-4) s(-1), so the K-d value is apparently in the range 0.05-0.40 mu M. The spectral changes observed immediately after quinol-induced turnover, or during steady-state turnover induced by hydrazine or by carbon monoxide, are qualitatively the same as those induced by H2O2 though of lower amplitude. H2O2 addition perturbs the hydrazine-induced or CO-induced steady states by increasing the amplitude of the spectral changes, but there is no qualitative change. From this observation, and the 1:1 stoichiometry of the reaction, we conclude that the intermediate induced by H2O2, which we term F-., requires donation of only two electrons to the enzyme from an external source.