Polyphenol oxidase from Allium sp.

Polyphenol oxidase (PPO) was isolated from Allium sp. PPO showed activity to catechol and DL-dopa (K-m values were 25 mM for cathecol and 33 mM for DL-dopa; V-max values were 666 EU/mL . min for cathecol and 166 EU/mL . min for DL-dopa). Catechol was the most suitable substrate for Allium sp. PPO (lowest K-m value). The optimum pH for the PPO was 7.5 on substrates catechol and DL-dopa. Heat inactivation studies showed temperature >40 degrees C resulted in loss of enzyme activity. Heating for 30 min at 40 degrees C did not cause a significant loss of enzymatic activity. Allium sp. PPO was significantly inhibited in the presence of ascorbic acid, 2-mercaptoethanol, and sodium metabisulfide.