Characteristics Of Polyphenol Oxidase Research Articles

Purification and Biochemical Characterization of Polyphenol Oxidase Extracted from Wheat Bran (Wan grano).

Currently, little is known about the characteristics of polyphenol oxidase from wheat bran, which is closely linked to the browning of wheat product. The wheat PPO was purified by ammonium sulfate precipitation, DEAE-Sepharose ion-exchange column, and Superdex G-75 chromatography column. Purified wheat PPO activity was 11.05-fold higher, its specific activity was 1365.12 U/mg, and its yield was 8.46%. SDS-PAGE showed that the molecular weight of wheat PPO was approximately 21 kDa. Its optimal pH and temperature were 6.5 and 35 °C for catechol as substrate, respectively. Twelve phenolic substrates from wheat and green tea were used for analyzing the substrate specificity. Wheat PPO showed the highest affinity to catechol due to its maximum Vmax (517.55 U·mL-1·min-1) and low Km (6.36 mM) values. Docking analysis revealed strong affinities between catechol, gallic acid, EGCG, and EC with binding energies of -5.28 kcal/mol, -4.65 kcal/mol, -4.21 kcal/mol, and -5.62 kcal/mol, respectively, for PPO. Sodium sulfite, ascorbic acid, and sodium bisulfite dramatically inhibited wheat PPO activity. Cu2+ and Ca2+ at 10 mM were considered potent activators and inhibitors for wheat PPO, respectively. This report provides a theoretical basis for controlling the enzymatic browning of wheat products fortified with green tea.

Purification and characterization of polyphenol oxidase (PPO) from water yam (Dioscorea alata)

ABSTRACTPolyphenol oxidase (PPO) is responsible for the enzymatic browning of fruits and vegetables, and thus has negative effects on the quality of food. In this study, extraction and purification of PPO from water yam was performed successfully, and the characteristics of PPO and inhibitors of enzyme activity were analysed. The results showed that PPO activity improved by 4.58-fold through the DEAE-Sepharose and Superdex G-75 purification technique, which reached electrophoretic purity. The enzyme molecular weight was estimated to be 32 kDa. The optimum pH and temperature values of PPO were 6.0 and 35°C, respectively, and it was not thermostable at higher temperatures. PPO had the highest substrate affinity towards catechol (Km = 27.82 mmol/L and Vmax = 1.464 △A/min). The most effective inhibitor was L-cysteine followed by ascorbic acid and sodium sulfite.

POLYPHENOL OXIDASE AND PEROXIDASE ACTIVITIES IN MANGOES STORED AT CHILLING TEMPERATURE

Mangoes are tropical fruits and therefore chilling-sensitive. Storage of these fruits at low temperature can cause chilling injury. Since peroxidase (POD) and polyphenol oxidase (PPO) are involved in the metabolism of phenolic compounds and in the development of several physiological disorders, as chilling injury (CI), we have undertaken to study the effect of low temperature storage on the activation of these enzymes in mangoes. Some characteristics of PPO and POD were investigated. Maximum activities of PPO were found at pH 8,0 and 7,5 for skin and pulp respectively. In both cases the optimum temperature was 40°C. Maximum activities of POD were found at pH 5,0 while the optimum temperatures were 60°C and 30°C for peel and pulp. 'Kent', 'Keitt' and 'Manila' mangoes were stored at 5°C during 25 days and rewarmed at 20°C until ripening. CI symptoms in peel were more severe than in pulp. PPO activity increased in peel and pulp of mangoes stored at 5°C. PDO activity increased in pulp and showed lower activity in peel. Correlation was found between CI index and PPO activity in mangoes.

Polyphenol Oxidase: Characteristics and Mechanisms of Browning Control

Polyphenol oxidase, a copper-containing metalloprotein, catalyzes the oxidation of phenolic compounds to quinones, which produce brown pigments in wounded tissues. This enzymatic mechanism causes post harvest losses and mainly affects tropical fruits. In this article, some characteristics of polyphenol oxidase from different plants are reviewed and information about conventional and alternative methods to inactivate this enzyme is presented. Characterization of the polyphenol oxidase could help to develop or to choose more effective methods for controlling browning of vegetables and products.

Effects of aqueous chlorine dioxide treatment on polyphenol oxidases from Golden Delicious apple

Effects of chlorine dioxide (ClO 2) treatment on the activity and characteristics of polyphenol oxidase (PPO) in Golden Delicious apples were studied. The treatment with 50 mg/l ClO 2 for 1 h did not affect some characteristics of the PPO, including its optimum pH value (5.0) and temperature (40 °C) as well as the maximum absorption wavelength (412 nm) of the final products. With increasing ClO 2 concentrations from 0 to 100 mg/l, the V max ′ value reduced and K m ′ value changed irregularly. When the concentration of ClO 2 increased from 0 to 60 mg/l, residual PPO activities significantly decreased, showing a negative linear-correlation with ClO 2 concentration. For 10 and 50 mg/l ClO 2 treatments, partial inhibition of PPO was achieved within 0.5 h and the PPO activities did not significantly decrease after 0.5 h. The inhibition and inactivation of PPO by ClO 2 treatment were observed at processing temperatures (30 and 70 °C) and storing temperatures (20, 0–4, and −18 °C).

PARTIAL PURIFICATION AND CHARACTERIZATION OF POLYPHENOL OXIDASE FROM FRESH-CUT CHINESE WATER CHESTNUT

The characteristics of polyphenol oxidase (PPO) from Chinese water chestnut (CWC) and its potential inhibitors for browning reactions were investigated. PPO was isolated from fresh-cut CWC and was purified on a Sephadex G-100 column, with a yield of total activity close to 10%. The molecular weight, Michaelis constant (K[subscript m]), substrate specificity, optimal pH and temperature of CWC PPO were examined. Kinetic studies indicated that the K[subscript m] and V[subscript max] values of CWC PPO for catechol were 10.32 mmol[solidus]L and 6.452 [multiplication] 10[superscript 4] U[solidus]min, respectively. The optimal pH and temperature for CWC PPO was 6.5 and 40C, respectively. Among the browning inhibitors tested, 4-hexylresorcinol, at a concentration of 0.3 mmol[solidus]L, showed the strongest inhibition (70%) against the PPO activity of CWC, followed by 3.0 mmol[solidus]L N-acetyl-L-cysteine with an inhibition of 53%.