Characterization of polyphenol oxidase from blueberry (Vaccinium corymbosum L.)

Polyphenol oxidase (PPO) was extracted and characterized from high-bush blueberries. PPO showed an optimum activity at pH 6.1-6.3 and 35 degrees C, with the enzyme showing significant activity over a wide temperature range (25-60 degrees C). Catechol was the most readily oxidized substrate followed by 4-methylcatechol, DL-DOPA, and dopamine. Blueberry PPO showed a K-m of 15 mM and V-max of 2.57 Delta A(420) nm/min x 10(-1), determined with catechol. PPO was completely inactivated in 20 min at 85 degrees C, however, after 30 min at 75 degrees C it showed about 10% residual activity. Thermal treatment at 55 and 65 degrees C for 30 min resulted in the, partial inactivation of PPO. Ascorbic acid, sodium diethyldithiocarbamic acid, L-cysteine, and sodium metabisulfite were effective inhibitors of PPO at 1.0 mM. Benzoic acid and cinnamic acid series inhibitors showed relatively weak inhibition of PPO (21.8-27.6%), even at as high as 2.0 mM concentration. (C) 2016 Elsevier Ltd. All rights reserved.