Mechanism of inactivation of myeloperoxidase by 4-aminobenzoic acid hydrazide
Mechanism of inactivation of myeloperoxidase by 4-aminobenzoic acid hydrazide
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DOI：
10.1042/bj3210503
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发表时间：
1997-01-15
影响因子：
4.1
通讯作者：
Winterbourn, CC
中科院分区：
文献类型：
--
作者：
Kettle, AJ;Gedye, CA;Winterbourn, CC
次氯酸是中性粒细胞产生的最强氧化剂，可能导致这些炎症细胞介导的损伤。血红素酶髓过氧化物酶催化其从过氧化氢和氯化物的生产。4-氨基苯甲酸酰肼（ABAH）是一种有效的次氯酸生成抑制剂。在这项调查中，我们表明，在过氧化氢的存在下，ABAH不可逆地失活髓过氧化物酶。ABAH被髓过氧化物酶氧化，失活的动力学分析符合基于机制的抑制剂。失活加剧了过氧化氢的浓度大于50 μ M和氧气的情况下。单独使用过氧化氢导致最小程度的灭活。还原型谷胱甘肽抑制ABAH的氧化以及髓过氧化物酶的不可逆抑制。在氧气存在下，ABAH和过氧化氢最初将髓过氧化物酶转化为化合物III，随后失去血红素吸光度。在没有氧气的情况下，该酶被转化为亚铁髓过氧化物酶，其血红素基团被迅速破坏。我们建议，髓过氧化物酶氧化ABAH的自由基，减少酶的亚铁中间体。亚铁髓过氧化物酶与氧反应以允许酶周转，或与过氧化氢反应以产生不可逆失活。
Hypochlorous acid is the most powerful oxidant generated by neutrophils and is likely to contribute to the damage mediated by these inflammatory cells. The haem enzyme myeloperoxidase catalyses its production from hydrogen peroxide and chloride. 4-Aminobenzoic acid hydrazide (ABAH) is a potent inhibitor of hypochlorous acid production. In this investigation we show that, in the presence of hydrogen peroxide, ABAH irreversibly inactivates myeloperoxidase. ABAH was oxidized by myeloperoxidase, and kinetic analysis of the inactivation conformed to that for a mechanism-based inhibitor. Inactivation was exacerbated by concentrations of hydrogen peroxide greater than 50 mu M and by the absence of oxygen. Hydrogen peroxide alone caused minimal inactivation. Reduced glutathione inhibited the oxidation of ABAH as well as the irreversible inhibition of myeloperoxidase. In the presence of oxygen, ABAH and hydrogen peroxide initially converted myeloperoxidase into compound III, which susequently lost haem absorbance. In the absence of oxygen, the enzyme was converted into ferrous myeloperoxidase and its haem groups were rapidly destroyed. We propose that myeloperoxidase oxidizes ABAH to a radical that reduces the enzyme to its ferrous intermediate. Ferrous myeloperoxidase reacts either with oxygen to allow enzyme turnover, or with hydrogen peroxide to give irreversible inactivation.