Polyphenol oxidase from Dominga table grape.
Dominga grape polyphenol oxidase (PPO) was extracted using phase partitioning with Triton X-114. The enzyme was obtained in latent state and could be optimally activated by the presence of 0.2% sodium dodecyl sulfate (SDS) at pH 6.0. In the absence of SDS, the enzyme showed maximum activity at acid pH. The kinetic parameters of the enzyme at pH 3.0 and 6.0 in the presence of SDS were calculated. The effect of several inhibitors was studied, tropolone being the most effective with a K(i) value of 18 muM. The effect of cyclodextrins was also studied, and the complexation constant K(c) between G(2)-beta-cyclodextrins and 4-tert-butylcatechol was calculated using the enzymatic method (K(c) = 13960 M(-)(1)). The evolution of the color parameters (L, a, b) of liquefied grape berries was inhibited by inhibitors of PPO activity, such as diethyldithiocarbamate, metabisulfite, and G(2)-beta-cyclodextrins, indicating that enzymatic browning by PPO is the main process involved in the browning of Dominga grape juice at room temperature.
Núñez-Delicado
Estrella
E
Departamento de Ciencia y Tecnología de Alimentos, Universidad Católica San Antonio de Murcia, Avenida de los Jerónimos s/n, 30107 Guadalupe, Murcia, Spain. enunez@pdi.ucam.edu
Serrano-Megías
Marta
M
Pérez-López
Antonio José
AJ
López-Nicolás
José Manuel
JM
D004156:Catechol Oxidase / Q000302:isolation & purification* / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005638:Fruit / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015416:Maillard Reaction; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D027843:Vitis / Q000201:enzymology*
D004791:Enzyme Inhibitors; D012967:Sodium Dodecyl Sulfate; D004156:Catechol Oxidase