In vitro oxidation of hispidin and gallic acid by horseradish peroxidase

Gallic acid and hispidin have been previously described by us as inhibitors of horseradish peroxidase (Benarous, K., Benali, F. Z., Bekhaoua, I. C., and Yousfi, M. Journal of Biomolecular Structure & Dynamics, (2021) 39(18), 7168-7180). However, additional experiments have demonstrated that under the applied assay conditions both compounds are rapidly oxidized by this enzyme. After oxidation, the components of the reaction mixture undergo complex reactions giving products with much weaker absorption at the detection wavelength. This was interpreted by us as enzyme inhibition, which, however, is only apparent. In fact, the activity of horseradish peroxidase is not affected by these compounds, which was demonstrated by measurements of hydrogen peroxide consumption. Communicated by Ramaswamy H. Sarma

Automated summary

Gallic acid and hispidin were previously described as inhibitors of horseradish peroxidase, but additional experiments showed that both compounds are rapidly oxidized by the enzyme. Although it was interpreted as enzyme inhibition, the activity of horseradish peroxidase is not affected by these compounds.