In this study, invertase was immobilized in copolymer electrodes constructed. Three different types of polymethyl methacrylate-co-polymethyl thienyl methacrylate matrices were used to obtain copolymers that were characterized by FT-IR spectroscopy. Immobilization of enzymes was carried out by the entrapment of the enzyme in conducting polymer matrices during electrochemical polymerization of pyrrole through thiophene moieties of polymers. Immobilization of the enzyme was achieved by application of 1.0 V constant potential on a platinum electrode for 30 min in solution. The effects of temperature and pH on the activity of the enzyme electrodes were examined and operational stability studies were done. The changes in the maximum reaction rate and the variations in the Michaelis-Menten constant were studied. (C) 2005 Wiley Periodicals, Inc.