CRESOLASE ACTIVITY OF POTATO-TUBER PARTIALLY PURIFIED IN A 2-PHASE PARTITION SYSTEM

The cresolase activity of partially purified potato polyphenol oxidase extracted by a two-phase partition method in Triton X-114 (Sanchez-Fe rrer, A.; Laveda, F.; Garcia-Carmona, F. J. Agric. Food Chem. 1993, pr evious paper) has been characterized without using ascorbic acid. The purification method avoids the loss of cresolase activity described by other potato polyphenol oxidases. The activity was characterized by a lag period, whose duration depended on the substrate concentration, t he pH, and the presence of catalytic amounts of o-diphenol. By increas ing the concentration of o-diphenols, it was possible to evaluate the enzyme activation constant, K(act), which showed a value of 4.5 muM. A general kinetic mechanism for this enzyme is used to explain the loss of activity which normally occurs during potato tuber polyphenol oxid ase purification.