An approach was developed to screening organic compounds for putative activity of redox mediators of oxidoreductases, including laccases and peroxidases, applicable for xenobiotic degradation. The study was carried out with a homogenous laccase preparation from the basidiomycete Trametes hirsuta and horse-radish root peroxidase. Compounds belonging to 1-phenyl-3-methylpyrazolones were selected. Spectroscopic and electrochemical investigation of two of the compounds, sodium 1-phenyl-2,3-dimethyl-4-aminopyrazolon 5n(4)-methanesulfonate (PPNa) and 1-(3'-sulfophenyl)-3-methylpyrazolone (SPP), was performed. Electrochemical oxidation of both PPNa and SPP gave rise to high-potential intermediates capable of oxidizing veratryl alcohol; a lignin-modeling compound. Kinetic indices of these compounds were determined in enzymatic reactions with the presence of laccase. It was shown that enzymatic oxidation of SPP by laccase produced high-potential intermediates capable of oxidizing veratryl alcohol to veratric acid. Veratryl alcohol did not oxidize during enzymatic oxidation of SPP by peroxidase. This points to a difference between the mechanisms of enzymatic oxidation of PPNa and SPP by laccase and peroxidase.