Properties of a glucose oxidase covalently immobilized on amorphous AlPO4 support

Glucose oxidase (GOD) was covalently immobilized on amorphous ALPO(4) as we ll as on an ALPO(4)/clay mineral Sepiolite system. Immobilization of the en zyme was carried out through the epsilon -amino group of lysine residues th rough an aromatic Schiff's-base. Activation of the support was obtained aft er reaction of appropriate molecules with support surface -OH groups. The e nzymatic activities of native, and different immobilized GOD systems and fi ltrates, were followed by the amount of liberated D-gluconic acid obtained in the enzymatic beta -D-glucose oxidation with the aid of an automatic tit rator. The kinetic properties of native and immobilized GOD were obtained f or-glucose concentrations in the range of physiological conditions and at d ifferent working conditions such as' reaction temperature, reaction pH, and enzyme concentration. The binding percentage of enzymes was in the 50-80% range, with residual an d specific activities in the 65-80% and 90-150% ranges, respectively. No ch ange in the pH optimum and only slight changes in the V-max and K-M kinetic parameters with respect to native GOD were observed, so that not only was Little deactivation of enzyme obtained throughout the immobilization proces s but also that the stability of the covalently bound enzyme in the two sup ports appeared to have increased with respect to the soluble enzyme. GOD im mobilization also increased its efficiency and operational stability in rep eated uses on increasing the amount of immobilized enzyme. (C) 2001 Elsevie r Science B.V. All rights reserved.