Glucose isomerase (GI) was entrapped in three different hydrogels such as poly(acrylamide), semi-interpenctrating poly(acrylamide)/K-carrageenan, and poly(acrylamide)/alginate polymer networks. The values for pH optimum and temperature for free and immobilized glucose isomerase were found to be the same as 7.5 and 60 degrees C, respectively. The K-m values for free and immobilized enzyme in poly(acrylamide), poly(acrylamide)/K-carrageenan and poly(acrylamide)/alginate matrices were determined as 18.87, 1.22, 2.78, and 4.54 mg/mL, respectively, while the V-max values for the same systems calculated as 2.51, 0.63, 0.72, and 0.82 mg/mL min, respectively. The storage stability values of immobilized enzyme systems were observed as 81%. 33% and 32%, respectively, after 42 days. In addition to this, it was observed that, after 25th use in 5 days, the retained activities for immobilized enzyme in poly(acrylamide), and semi-interpenetrating polymer networks of poly(acrylamide)/K-carrageenan and poly(acrylamide)/alginate matrices were found as 98%, 71% and 72%, respectively. (c) 2005 Elsevier B.V. All rights reserved.