The role of peroxidase in the enzymatic oxidation of phenolic compounds to quinones fromLuffa aegyptiaca(gourd) fruit juice

Luffa aegyptiaca fruit juice was used as a low purity source of enzyme, which contained peroxidase activity of 180 IU/mL. The results of UV/VIS and IR studies suggested that L. aegyptiaca fruit juice works efficiently in the enzymatic conversion of phenolic compounds, namely guaiacol, m-cresol, p-cresol, o-cresol, anisole, resorcinol, catechol, pyrogallol, hydroquinone, veratryl alcohol and phoreguicinol to quinones at 30°C. The p-cresol and pyrogallol were converted to quinones more efficiently as compared to other phenolic compounds. Determination of enzymatic characteristic properties such as Michaelis–Menten constant (Km), temperature optima and pH optima using different phenolic compounds, indicated p-cresol as a potential substrate for the peroxidase enzyme assay at room temperature, whereas guaiacol, which is widely used as a substrate for enzyme assay, has a higher temperature optima at 60°C for its maximum catalytic activity. Enzyme activity is inhibited by sodium azide using different phenolic substrates in the reaction mixture.