Purification and partial biochemical characterization of polyphenol oxidase from mamey (Pouteria sapota) |
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Authors: | Palma-Orozco Gisela Ortiz-Moreno Alicia Dorantes-Alvarez Lidia Sampedro José G Nájera Hugo |
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Institution: | a Escuela Nacional de Ciencias Biológicas, Departamento de Ingeniería Bioquímica Instituto Politécnico Nacional, México, D.F., Mexico b Instituto de Física, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico c Universidad Autónoma Metropolitana - Cuajimalpa, Departamento de Ciencias Naturales, México, D.F., Mexico |
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Abstract: | While a long shelf life for fruit products is highly desired, enzymatic browning is the main cause of quality loss in fruits and is therefore a main problem for the food industry. In this study polyphenol oxidase (PPO), the main enzyme responsible for browning was isolated from mamey fruit (Pouteria sapota) and characterized biochemically. Two isoenzymes (PPO 1 and PPO 2) were obtained upon ammonium sulfate precipitation and hydrophobic and ion exchange chromatography; PPO 1 was purified up to 6.6-fold with 0.28% yield, while PPO 2 could not be characterized as enzyme activity was completely lost after 24 h of storage. PPO 1 molecular weight was estimated to be 16.1 and 18 kDa by gel filtration and SDS-PAGE, respectively, indicating that the native state of the PPO 1 is a monomer. The optimum pH for PPO 1 activity was 7. The PPO 1 was determined to be maximum thermally stable up to 35 °C. Kinetic constants for PPO 1 were Km = 44 mM and Km = 1.3 mM using catechol and pyrogallol as substrate, respectively. The best substrates for PPO 1 were pyrogallol, 4-methylcatechol and catechol, while ascorbic acid and sodium metabisulfite were the most effective inhibitors. |
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Keywords: | Sapote mamey (Pouteria sapota) Sapotaceae PPO purification Catechol Pyrogallol Polyphenol oxidase |
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