Oxidative 4-dechlorination of 2,4,6-trichlorophenol catalyzed by horseradish peroxidase

Abstract

The well-known and easily available horseradish peroxidase (HRP) catalyzes the H2O2-dependent oxidative 4-dechlorination of the pollutant 2,4,6-trichlorophenol, which is recalcitrant to many organisms except those producing ligninases. UV-visible spectroscopy and gas chromatography-mass spectrometry identified the oxidized reaction product as 2,6-dichloro-1,4-benzoquinone. NMR and IR spectroscopic data further supported the above characterization. Experimental evidence for the elimination of HCl from the substrate was acquired by detecting the decrease in pH of the reaction mixture, and by observing the presence of the beta-chlorocyclopentadienone cation fragment in the mass spectrum of 2,6-dichloro-1,4-benzoquinone. Consequently, nucleophilic attack by water on the 2,4,6-trichlorocyclohexadienone cation was proposed to give the final product. Our results indicate an oxidative dechlorination pathway catalyzed by HRP for 2,4,6-trichlorophenol, similar to that by extracellular lignin peroxidases. The relative catalytic efficiency of HRP seems higher than that of lignin peroxidases. The HRP-H2O2 catalytic system could be utilized in the degradation of polychlorinated phenols for industrial and biotechnological purposes.

TiO2-soybean peroxidase composite materials as a new photocatalytic system

“…In the case of the SBP/H 2 O 2 system, any other intermediate was identified, but the reaction mixture initially turns from colourless to yellow, indicating the probable production of 2,6-dichloro-1,4-benzoquinone, in agreement with previous data reported for the reaction catalyzed by lignine peroxidase [30] and horseradish peroxidase [31].…”

Unusual kinetic role of a water‐soluble iron(III) porphyrin catalyst in the oxidation of 2,4,6‐trichlorophenol by hydrogen peroxide

“…Based on the known mechanisms of phenol oxidations [25][26][27][28], it seems likely that the reaction produces a phenoxide radical via hydrogen atom abstraction from TCP in the rate-determining step. The phenoxide radical is then likely to react with hydrogen peroxide present in large excess and release chloride ion forming the product quinone in subsequent fast steps.…”

Oxidative degradation of Remazol Turquoise Blue G 133 by soybean peroxidase

“…The same experiment was repeated replacing RTB with 2,4,6-trichlorophenol (2,4,6-TCP) at the concentration of 1.17 × 10 −5 M. In this case we investigated the oxidative dechlorination of the 2,4,6-TCP following the formation of the final reaction product, 2,6-dichloro-1,4-benzoquinone, at 272 nm (ε 272 nm = 1.4 × 10 4 M −1 cm −1 [28]). …”