THE HALIDE-COMPLEXES OF MYELOPEROXIDASE AND THE MECHANISM OF THE HALOGENATION REACTIONS
THE HALIDE-COMPLEXES OF MYELOPEROXIDASE AND THE MECHANISM OF THE HALOGENATION REACTIONS
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DOI：
10.1016/0005-2744(80)90088-1
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发表时间：
1980-01-01
期刊：
影响因子：
--
通讯作者：
WEVER, R
中科院分区：
文献类型：
--
作者：
BAKKENIST, ARJ;DEBOER, JEG;WEVER, R
研究了向[人]髓过氧化物酶（EC 1.11.1.7）中加入卤化物所引起的光谱变化，并测定了酶-卤化物复合物的Kd。的Kd的pH依赖性表明，卤化物结合与髓过氧化物酶的质子化步骤。髓过氧化物酶催化一氯双甲酮的过氧化氯化和溴化。在低pH值下，氯化物作为相对于H2 O2的竞争性抑制剂;在较高pH值下，H2 O2抑制氯化反应。光谱可检测复合物的Kd和氯化物的Km远小于氯化物的抑制常数（Ki）。这些卤化反应是强烈的pH值依赖性的;氯化物的Km的对数随pH值线性变化。氯化和溴化反应的最佳pH值的位置是[卤化物]/[H2 O2]比的对数的线性函数。氯化和溴化反应的机制建议与底物抑制H2 O2和卤化物。
The spectral changes caused by the addition of halides to [human] myeloperoxidase (EC 1.11.1.7) were investigated and the Kd of the enzyme-halide complexes were determined. The pH dependence of the Kd indicates that halide binding is associated with a protonation step in myeloperoxidase. Myeloperoxidase catalyzes the peroxidative chlorination and bromination of monochlorodimedone. At low pH, chloride acts as a competitive inhibitor with respect to H2O2; at higher pH, H2O2 inhibits the chlorination reaction. The Kd of the spectroscopically detectable complex and the Km for chloride are considerably smaller than the inhibition constant (Ki) for chloride. These halogenation reactions are strongly pH dependent; the logarithm of the Km for chloride varies linearly with pH. The position of the pH optimum of the chlorination and bromination reaction is a linear function of the logarithm of the [halide]/[H2O2] ratio. A mechanism of the chlorination and bromination reaction is suggested with substrate inhibition for H2O2 and the halide.