Oxidation of 2,4-dichlorophenol catalyzed by horseradish peroxidase: characterization of the reaction mechanism by UV-visible spectroscopy and mass spectrometry.
The hydrogen peroxide-oxidation of 2,4-dichlorophenol catalyzed by horseradish peroxidase has been studied by means of UV-visible spectroscopy and mass spectrometry in order to clarify the reaction mechanism. The dimerization of 2,4-dichlorophenol to 2,4-dichloro-6-(2,4-dichlorophenoxy)-phenol and its subsequent oxidation to 2-chloro-6-(2,4-dichlorophenoxy)-1,4-benzoquinone together with chloride release were observed. The reaction rate was found to be pH-dependent and to be influenced by the pK(a) value of 2,4-dichlorophenol. The dissociation constants of the 2,4-dichlorophenol/horseradish peroxidase (HRP) adduct at pH 5.5 and 8.5 were also determined: their values indicate the unusual stability of the adduct at pH 5.5 with respect to several adducts of HRP with substituted phenols.
Laurenti
Enzo
E
Dipartimento di Chimica IFM, Università di Torino, Via P Giuria 7, 10125 Turin, Italy. enzo.laurenti@unito.it
Ghibaudi
Elena
E
Ardissone
Silvia
S
Ferrari
Rosa Pia
RP
D002384:Catalysis; D002733:Chlorophenols / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D002733:Chlorophenols; D006735:Horseradish Peroxidase; C004762:2,4-dichlorophenol