Büttner Enrico, Ullrich René, Strittmatter Eric, Piontek Klaus, Plattner Dietmar A, Hofrichter Martin, Liers Christiane
TU Dresden, International Institute Zittau, Markt 23, 02763 Zittau, Germany.
University of Freiburg, Institute of Organic Chemistry, Albertstrasse 21, 79104 Freiburg, Germany.
Arch Biochem Biophys. 2015 May 15;574:86-92. doi: 10.1016/j.abb.2015.03.003. Epub 2015 Mar 18.
Substantial conversion of nitrophenols, typical high-redox potential phenolic substrates, by heme peroxidases has only been reported for lignin peroxidase (LiP) so far. But also a dye-decolorizing peroxidase of Auricularia auricula-judae (AauDyP) was found to be capable of acting on (i) ortho-nitrophenol (oNP), (ii) meta-nitrophenol (mNP) and (iii) para-nitrophenol (pNP). The pH dependency for pNP oxidation showed an optimum at pH 4.5, which is typical for phenol conversion by DyPs and other heme peroxidases. In the case of oNP and pNP conversion, dinitrophenols (2,4-DNP and 2,6-DNP) were identified as products and for pNP additionally p-benzoquinone. Moreover, indications were found for the formation of random polymerization products originating from initially formed phenoxy radical intermediates. Nitration was examined using (15)N-labeled pNP and Na(14)NO2 as an additional source of nitro-groups. Products were identified by HPLC-MS, and mass-to-charge ratios were evaluated to clarify the origin of nitro-groups. The additional nitrogen in DNPs formed during enzymatic conversion was found to originate both from (15)N-pNP and (14)NO2Na. Based on these results, a hypothetical reaction scheme and a catalytically responsible confine of the enzyme's active site are postulated.
到目前为止，仅报道过木质素过氧化物酶（LiP）能大量转化典型的高氧化还原电位酚类底物硝基酚。但还发现黑木耳的一种染料脱色过氧化物酶（AauDyP）能够作用于：（i）邻硝基苯酚（oNP）、（ii）间硝基苯酚（mNP）和（iii）对硝基苯酚（pNP）。对pNP氧化的pH依赖性表明在pH 4.5时存在最佳值，这是DyP和其他血红素过氧化物酶转化苯酚的典型特征。在oNP和pNP转化的情况下，二硝基苯酚（2,4 - DNP和2,6 - DNP）被鉴定为产物，对于pNP还生成了对苯醌。此外，发现有迹象表明最初形成的苯氧基自由基中间体形成了无规聚合产物。使用（15）N标记的pNP和Na（14）NO2作为硝基的额外来源来研究硝化作用。通过HPLC - MS鉴定产物，并评估质荷比以阐明硝基的来源。发现在酶促转化过程中形成的DNP中的额外氮既来自（15）N - pNP，也来自（14）NO2Na。基于这些结果，推测了一个假设的反应方案以及该酶活性位点的催化责任区域。
