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| Neves,Valdir Augusto; Picchi,Douglas Gatte; Silva,Maraiza Aparecida da. |
| Polyphenoloxidase (PPO; EC 1.14.18.1) extracted from Mentha arvensis leaves was isolated by (NH4)2SO4 precipitation and extensive dialysis. Its optimum pH and temperature varied with the substrate. The PPO showed activity with various diphenols. Km values were found 0.825, 0.928 and 7.41mM for caffeic acid, 4-methylcatechol and catechol, respectively. On heat-inactivation, half of the activity was lost after 60 and 15 sec at 70 and 75ºC, respectively. Measuring of residual activity showed a stabilizing effect of sucrose at various temperatures with activation energy (Ea) for inactivation increasing with sucrose concentration from 0 to 40% (w/w). Ea values of 78.13; 80.37; 82.79 and 81.00 kJ/Mol were found for 0, 15; 30 and 40% sucrose, respectively. PPO... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Polyphenoloxidase; Mentha arvensis; Characterization; Heat inactivation; Inhibitors. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132009000400025 |
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| Neves,Valdir Augusto; Lourenço,E. J.. |
| Peroxidase from peach fruit was purified 28.9-fold by DEAE-cellulose, Sephadex G-100 and hydroxylapatite chromatography. The purified enzyme showed only one peak of activity with an optimum pH of 5.0 and temperature of 40ºC. The calculated activation energy (Ea) for the reaction was 7.97 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 80ºC with a fast inactivation at 80ºC. PAGE of the inactivation course at 70ºC showed only one band of activity. Different sugars increased the heat stability of the activity in the following order: sucrose>lactose>glucose>fructose. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (10 to 40%, w/w) with the Ea for inactivation... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Peach peroxidase; Purification; Heat stability; Regeneration. |
| Ano: 1998 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89131998000200002 |
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| Neves,Valdir Augusto. |
| Soluble, ionically bound peroxidase (POD) and polyphenoloxidase (PPO) were extracted from the pulp of peach fruit during ripening at 20°C. Ionically bound form was purified 6.1-fold by DEAE-cellulose and Sephadex G-100 chromatography. The purified enzyme showed only one peak of activity on Sephadex G-100 and PAGE revealed that the enzyme was purified by the procedures adopted. The purified enzyme showed a molecular weight of 29000 Da, maximum activity at pH 5.0 and at 40ºC. The calculated apparent activation energy (Ea) for the reaction was10.04 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 75ºC with a fast inactivation at 75ºC. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Peach peroxidases; Ripening; Purification; Kinetics; Heat stability. |
| Ano: 2002 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132002000100002 |
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