Purification and characterization of polyphenol oxidase from Ferula sp.

Polyphenol oxidase (PPO) of several Ferula sp. was extracted and purified through (NH₄)₂SO₄ precipitation, dialysis, and gel filtration chromatography. Leaf and stem extracts were used for the determination of enzyme properties. Optimum conditions, for pH, temperature, and ionic strength were determined. The best substrates of PPO were catechol for leaf and (−) epicatechin for stem samples. Optimum pH and temperature were determined. K_M and V_max values were 2.34 × 10⁻³ M and 8541 EU/ml for catechol, and 2.89 × 10⁻³ M and 5308 EU/ml for (−) epicatechin. The most effective inhibitor was sodium diethyl dithiocarbamate for leaf samples and sodium metabisulphite for stem samples. Both inhibitors indicated competitive reactions. PPO showed irreversible denaturation after 40 min at 60 °C.