INFLUENCE OF IMMOBILIZATION ON THE THERMAL INACTIVATION OF YEAST INVERTASE

Different immobilized preparations of yeast invertase were studied for the purpose of refining the mechanism of inactivation of free enzyme. Four immobilization techniques were applied: biospecific adsorption o n the concanavalin A-bead cellulose matrix; covalent immobilization on the activated bead cellulose matrix; and cross-linking of the aforeme ntioned preparations with glutaraldehyde. All preparations were assess ed with respect to the activity loss during immobilization, thermal st ability, and inactivation kinetics. For each preparation, a correspond ing inactivation mechanism was verified using the multitemperature dat a evaluation. The preparations, whose biological activities were stron gly modified during immobilization, were shown to be unsuitable for el ucidating the inactivation mechanism of free invertase. The biospecifi cally adsorbed invertase on the concanavalin A-bead cellulose matrix m et all criteria for a preparation that should be a convenient model of free enzyme. This preparation was found to inactivate through a three -step series mechanism with the activation energies of individual reac tions at 304, 833, and 675 kJ mol(-1). The results obtained in this st udy complemented an existing mechanism of the inactivation of free inv ertase. (C) 1997 Elsevier Science Inc.