title: Characterization of polyphenol oxidase from blueberry (Vaccinium corymbosum L.).
abstract: Polyphenol oxidase (PPO) was extracted and characterized from high-bush blueberries. PPO showed an optimum activity at pH 6.1-6.3 and 35°C, with the enzyme showing significant activity over a wide temperature range (25-60°C). Catechol was the most readily oxidized substrate followed by 4-methylcatechol, DL-DOPA, and dopamine. Blueberry PPO showed a Kmof 15mM and Vmaxof 2.57 ΔA420nm/min×10-1, determined with catechol. PPO was completely inactivated in 20min at 85°C, however, after 30minat 75°C it showed about 10% residual activity. Thermal treatment at 55 and 65°C for 30min resulted in the partial inactivation of PPO. Ascorbic acid, sodium diethyldithiocarbamic acid, L-cysteine, and sodium metabisulfite were effective inhibitors of PPO at 1.0mM. Benzoic acid and cinnamic acid series inhibitors showed relatively weak inhibition of PPO (21.8-27.6%), even at as high as 2.0mM concentration.
authors.affiliation: Department of Food Science & Human Nutrition, Michigan State University, East Lansing, MI 48824, USA. Electronic address: siddiq@msu.edu.
authors.forename: M
authors.initials: M
authors.lastname: Siddiq
authors.affiliation: Department of Food Science & Human Nutrition, Michigan State University, East Lansing, MI 48824, USA; Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Dolan
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D029798:Blueberry Plants / Q000201:enzymology* / Q000254:growth & development; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D004156:Catechol Oxidase / Q000187:drug effects / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism; D003116:Color; D003545:Cysteine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013379:Substrate Specificity; D013447:Sulfites / Q000494:pharmacology; D013696:Temperature
chemical_list: D000975:Antioxidants; D016085:Bronchoconstrictor Agents; D002396:Catechols; D013447:Sulfites; C018599:4-methylcatechol; C005200:sodium metabisulfite; D004156:Catechol Oxidase; D003545:Cysteine; C034221:catechol; D001205:Ascorbic Acid
keywords: Blueberry; Inhibition; Kinetics properties; Polyphenol oxidase; pH and temperature optima