Enhanced enzymatic transformation of 1-naphthol in the presence of catechol by peroxidase

Effect of catechol on 1-naphthol transformation by horse radish peroxidase (HRP) was examined. The impact of catechol to 1-naphthol ratio, enzyme activity, pH, and reaction time in solution were studied. The results obtained indicated that, in the presence of catechol, 1-naphthol transformation by peroxidase shows enhancement greater than that in an equivalent catechol free system. Only 27% of 1-naphthol (0.3 mM) was able to transform when catechol was absent in solution, but reached 79% in its presence (3.0 mM) in 0.1M sodium phosphate buffer (pH 7.0), and 0.3 mM H₂O₂ by peroxidase (0.5 unit/mL) after 3 h. The 1-naphthol transformation rate was accelerated by increase of pH or HRP concentration. High-performance liquid chromatography analysis was performed to characterize transformation products based on their relative polarities, and molecular weights of products were identified by mass spectrometry. The transformation products were found to be (hydroxy) naphthoquinones, 1-naphthol: hydroxy-naphthoquinone, and 1-naphthol oligomers (dimer, trimer, tetramer) with the molecular weights (m/z) ranging 100-600. Liquid chromatography-tandem mass spectrometry technique, to the best of our knowledge, was used for the first time to elucidate the product structure at m/z 191. The study shows that 1-naphthol is transformed rapidly by peroxidase when catechol is present, which could be useful information for improving the efficiencies of decontamination techniques.