Resumen

GASULL, Estela  y  BECERRA, Daniela. Characterization of Polyphenyloxidase Extracted from Pears (cv. Packam´s Triumph) and Apples (cv . Red Delicious). Inf. tecnol. [online]. 2006, vol.17, n.6, pp.69-74. ISSN 0718-0764.  http://dx.doi.org/10.4067/S0718-07642006000600012.

A study was made of the properties of polyphenyloxidase (PPO) extracted from Packam´s Triumph pears and Red Delicious apples. Optimum pH and temperature were 6.5 and 25°C for pears, pH 7 and 30°C for apples, with 50 mM catechol in phosphate buffer as substrate. K_M values were 13.24 mM for pears and 232.80 mM for apples, whereas V_max values were 1590 U/mL E for pears, and 5464 U/mL E for apples, using 50 mM catechol as a substrate. Three PPO inhibitors were tested in this study with the most effective inhibitor being ascorbic acid. Kinetic studies showed that the thermal inactivation of PPO followed first-order kinetics. The activation enthalpy (H#^#) and activation entropy (S#^#) for PPO heat inactivation in pears was 15309 J/Mol and -102 J/K Mol respectively. In apples the H^## was 11582 while the S^## was -196 J/K Mol.

Palabras clave : polyphenyloxidase; enzymatic kinetics; pears; apples; thermal inactivation.