Peroxidase catalyzed nitration of tryptophan derivatives - Mechanism, products and comparison with chemical nitrating agents
Peroxidase catalyzed nitration of tryptophan derivatives - Mechanism, products and comparison with chemical nitrating agents
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DOI：
10.1111/j.1432-1033.2004.04219.x
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发表时间：
2004-07-01
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影响因子：
--
通讯作者：
Monzani, E
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文献类型：
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作者：
Sala, A;Nicolis, S;Monzani, E
用乳过氧化物酶和辣根过氧化物酶研究了色氨酸衍生物的酶促硝化反应，并与二氧化氮和过氧亚硝酸根的化学硝化反应进行了比较。产物混合物的HPLC、质谱和NMR分析清楚地表明，硝化发生在吲哚环的4-、6-、7-和N-1位，亚硝化发生在N-1位。对过氧化物酶/NO2-/H2 O2系统进行的动力学研究表明，所有色氨酸衍生物的底物饱和行为。速率对亚硝酸盐浓度的依赖性被认为是线性与辣根过氧化物酶，而它表现出饱和行为与乳过氧化物酶。产物混合物的组成取决于硝化剂。虽然4-硝基、6-硝基、7-硝基和N-1-硝基衍生物的产生遵循类似的趋势，表明它们是根据类似的机理形成的，但是当通过过氧化物酶/H2 O2/亚硝酸盐系统进行色氨酸修饰时，N-1-亚硝基衍生物和其它衍生物之间的比率显著取决于亚硝酸盐浓度。数据分析表明，在低亚硝酸盐浓度的酶反应发生通过经典的过氧化物酶循环。在高亚硝酸盐浓度下，反应通过不同的中间体进行，我们假设该中间体是蛋白质结合的过氧亚硝酸盐物质。
The enzymatic nitration of tryptophan derivatives by oxidation of nitrite has been studied using lactoperoxidase and horseradish peroxidase, and compared with the chemical nitration produced by nitrogen dioxide and peroxynitrite. HPLC, mass spectra and NMR analysis of the mixture of products clearly show that nitration occurs at position 4-, 6-, 7-, and N-1 of the indole ring, and nitrosation at position N-1. Kinetic studies performed on peroxidase/NO2-/H2O2 systems showed substrate saturation behavior with all the tryptophan derivatives employed. The rate dependence on nitrite concentration was found to be linear with horseradish peroxidase while it exhibited saturation behavior with lactoperoxidase. The composition of the product mixture depends on the nitrating agent. While the production of 4-nitro, 6-nitro, 7-nitro and N-1-nitro derivatives follows a similar trend, indicating that they are formed according to a similar mechanism, the ratio between the N-1-nitroso derivative and other derivatives depends markedly on the nitrite concentration when tryptophan modification is performed by the peroxidase/H2O2/nitrite systems. Analysis of the data indicates that at low nitrite concentration the enzymatic reaction occurs through the classical peroxidase cycle. At high nitrite concentration the reaction proceeds through a different intermediate that we assume to be a protein bound peroxynitrite species.