Peroxynitrite reaction with heme proteins
Peroxynitrite reaction with heme proteins
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DOI：
10.1006/niox.1999.0217
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发表时间：
1999-01-01
影响因子：
3.9
通讯作者：
Ullrich, V
中科院分区：
文献类型：
--
作者：
Mehl, M;Daiber, A;Ullrich, V
我们报道过低水平的过氧亚硝酸盐 (PN) 可通过酪氨酸残基的硝化导致血红素硫醇蛋白前列环素 (PGI(2)) 合酶失活。为了证明铁催化作用的参与，我们研究了 PN 与微过氧化物酶和 P450(nor)（一种已知结构的血红素硫醇蛋白）的相互作用。光谱和动力学分析得出结论，铁基二氧化氮络合物作为中间体，在过量 PN 存在下分解，形成双氧、亚硝酸盐和硝酸盐。这发生在使用 P450(nor) 比使用微过氧化物酶更有效的催化循环中。如果将苯酚添加到PN和铁络合物的反应混合物中，则与不含金属的体系相比，羟基化苯酚与硝化苯酚的比率降低。苯酚与双氧的形成竞争，这表明 Ferr1 中间体参与了这两种途径。因此，可以推测 Ferr1 络合物与苯酚反应生成苯氧基自由基，苯氧基自由基在二氧化氮存在下被硝化，但不会像不含金属的 PN 那样生成羟基化产物。或者，二氧化氮复合物可以将第二个 PN 分子氧化成自由基 。 OONO，可分解为分子氧和NO。后者与剩余的形成N2O3。 NO2自由基。第三条途径包括异构化为硝酸盐，这也由血红素蛋白催化，因为在与过量 PN 的催化反应过程中亚硝酸盐/硝酸盐的比例没有显着变化，我们的数据解释了 PGI(2)-合酶的硝化机制，表明 P450(nor) 作为 PN 清除剂的作用，并有利于血红素-硫醇盐复合物捕获 PN，(C) 1999 学术按。
We have reported that low levels of peroxynitrite (PN) can cause inactivation of the heme-thiolate protein prostacyclin (PGI(2))-synthase by nitration of a tyrosine residue. To prove that iron catalysis is involved we studied the interaction of PN with microperoxidase and P450(nor), a heme-thiolate protein of known structure. Spectral and kinetic analyses allow to conclude on a ferryl nitrogen dioxide complex as an intermediate which decomposes in the presence of an excess of PN under formation of dioxygen, nitrite, and nitrate. This occurs in a catalytic cycle which was more efficient with P450(nor) than with microperoxidase. If phenol was added to the reaction mixtures of PN and the ferric complexes the ratio of hydroxylated to nitrated phenols decreased compared to the metal-free system. Phenol competed with the formation of dioxygen indicating that the ferryl intermediate was involved in both pathways, One therefore can postulate that the ferryl complex reacts with phenol to give the phenoxyradical which is nitrated in the presence of nitrogen dioxide but does not give hydroxylated products as with metal-free PN. Alternately, the ferryl nitrogen dioxide complex can oxidize a second PN molecule to the radical, . OONO, which can decompose to dioxygen and NO. The latter forms N2O3 with the remaining . NO2 radical. A third pathway consists in the isomerization to nitrate which also is catalyzed by the heme proteins since the ratio of nitrite/nitrate does not change significantly during the catalytic reaction with excess of PN, Our data explain the mechanism of nitration of PGI(2)-synthase, suggest a role of P450(nor) as a PN scavenger, and favor heme-thiolate complexes for trapping PN, (C) 1999 Academic Press.