Hülya Yagar, Ayten Sagiroglu
Trakya University, Department of Chemistry, 22030 EDIRNE-TURKEY

Abstract
Polyphenol oxidase enzyme purified partially from quince (Cydonia oblonga) was immobilized on alumina (Al2O3) by simple adsorption at pH 6.8. The properties of immobilized enzyme were compared to those of the free enzyme. Optimum pH (8.5) and temperature (45 °C) were determined, showing the alteration of pH and temperature profiles by immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrate and it was established that affinity was highest for catechol. Km constant was 5 mM for catechol. Thermal and storage stability were carried out. It was observed that the immobilized enzyme had storage stability for a period of one year.