Ethyl hydroperoxide-dependent metabolism of N,N-dimethyl-p-anisidine catalysed by lactoperoxidase.
1. Chemical oxidation of N,N-dimethyl-p-anisidine (DMA) with bromine at pH 5-8 gave p-N,N-dimethylaminophenoxy radical irrespective of the DMA/Br2 ratio (1 to 100), whereas the ethyl hydroperoxide-supported oxidation of DMA catalysed by lactoperoxidase gave the phenoxy radical or the cation radical of DMA depending upon the concentration of DMA. 2. The amount of p-benzoquinone produced by the chemical oxidation increased steeply with an increase in pH above 6.0, whereas that produced by the lactoperoxidase-ethyl hydroperoxide-bromide system exhibited a pH optimum centred around pH 6.0. When the concentration of DMA was increased 10-fold, the enzymic formation of p-benzoquinone greatly decreased, whereas that of formaldehyde increased. 3. The rate of formation of the oxidized bromine species by the lactoperoxidase-ethyl hydroperoxide-bromide system showed a similar pH-profile to the formation of p-benzoquinone. 4. The oxidized bromine species is considered to be the predominant oxidizing agent in the lactoperoxidase-ethyl hydroperoxide-bromide system at pH 6.0 and below. The decrease in the amount of p-benzoquinone formed, and the increase in the amount of formaldehyde formed, by the lactoperoxidase-ethyl hydroperoxide-bromide system with increasing concentration of DMA, were interpreted in terms of competition between bromide and DMA for the reaction with compound I of lactoperoxidase.
Sayo
H
H
Faculty of Pharmaceutical Sciences, Kobe-Gakuin University, Japan.
Saito
M
M
D000814:Aniline Compounds / Q000378:metabolism*; D000818:Animals; D016227:Benzoquinones; D001966:Bromine; D002417:Cattle; D005557:Formaldehyde / Q000378:metabolism; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007784:Lactoperoxidase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism
D000814:Aniline Compounds; D016227:Benzoquinones; D005609:Free Radicals; D010545:Peroxides; D011809:Quinones; C025577:ethyl hydroperoxide; D005557:Formaldehyde; C004532:quinone; C050795:N,N-dimethyl-4-anisidine; D007784:Lactoperoxidase; D010544:Peroxidases; D001966:Bromine