title: Oxidation and nitration of mononitrophenols by a DyP-type peroxidase.
abstract: 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.
authors: TU Dresden, International Institute Zittau, Markt 23, 02763 Zittau, Germany.
authors: Enrico
authors: E
authors: Büttner
authors: TU Dresden, International Institute Zittau, Markt 23, 02763 Zittau, Germany.
authors: René
authors: R
authors: Ullrich
authors: University of Freiburg, Institute of Organic Chemistry, Albertstrasse 21, 79104 Freiburg, Germany.
authors: Eric
authors: E
authors: Strittmatter
authors: University of Freiburg, Institute of Organic Chemistry, Albertstrasse 21, 79104 Freiburg, Germany.
authors: Klaus
authors: K
authors: Piontek
authors: University of Freiburg, Institute of Organic Chemistry, Albertstrasse 21, 79104 Freiburg, Germany.
authors: Dietmar A
authors: DA
authors: Plattner
authors: TU Dresden, International Institute Zittau, Markt 23, 02763 Zittau, Germany.
authors: Martin
authors: M
authors: Hofrichter
authors: TU Dresden, International Institute Zittau, Markt 23, 02763 Zittau, Germany. Electronic address: christiane.liers@tu-dresden.de.
authors: Christiane
authors: C
authors: Liers
mesh_terms: D003116:Color; D004396:Coloring Agents / Q000378:metabolism; D062105:Molecular Docking Simulation; D009566:Nitrates / Q000378:metabolism*; D009596:Nitrophenols / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004396:Coloring Agents; D009566:Nitrates; D009596:Nitrophenols; D010544:Peroxidases
keywords: Dye-decolorizing peroxidases; Nitration; Nitrite; Nitrophenol; One-electron oxidation