Enzymatic degradation of 2,6-dichlorophenol by horseradish peroxidase: UV-visible and mass spectrometry characterization of the reaction products [corrected].

The reaction mechanism of the oxidation of 2,6-dichlorophenol (2,6-DCP) by horseradish peroxidase (HRP) and H2O2 has been investigated and the reaction products have been characterized by UV-visible and mass spectrometry. Evidence for the dimerization of 2,6-DCP to 3,3',5,5'-tetrachloro-4,4'-dihydroxybiphenyl and the subsequent fast oxidation of this product to the corresponding 3,3',5,5'-tetrachlorodiphenoquinone have been collected. The reaction rate was found to decrease markedly as soon as the pH was raised, with a clear inflection point at pH congruent with 6.6-6.9; it also resulted independent from H2O2 concentration. Since the pK(a) for 2,6-DCP is 6.80, the reaction rate might be influenced by the protonation state of the substrate.