Polyphenol Oxidase from Bean Sprouts ( Glycine max L.)

Polyphenol oxidase (PPO) was purified and characterized from bean sprouts by ammonium sulfate precipitation, DEAE‐Toyopearl 650M, CM‐Toyopearl 650M, SuperQ‐Toyopearl 650S and QAE‐Toyopearl 550C column chromatographies. Substrate staining of the crude extract on electrophoresis showed the presence of 2 isozymic forms of this enzyme. The molecular weight of the purified enzyme was estimated to be about 54 kDa. The optimum pH was 9.0 and optimum temperature 40 °C. Heat inactivation occurred about 30 °C. PPO showed activity to catechol, pyrogallol and dopamine. These compounds such as ascorbic acid, L‐cysteine, 2‐mercaptoethanol, and glutathione used was the effective inhibitor. Enzyme activity was maintained for 7 d at 4 °C but suddenly decreased after 8 d.