Horseradish peroxidase (HRP), which catalyzes oxidation reduction reactions of large number of substrates, was entrapped in K-carrageenan beads using polyethyleneimine as hardening agent. The heat and storage stability was found to be better for entrapped horseradish peroxidase than free enzyme. The entrapped enzyme showed 50% retention of its activity after 4 cycles. Effective diffusion coefficient for diffusion of hydroquinone into K-carrageenan beads was found to be 0.27 X 10(-10) m(2)/s during enzyme-catalyzed oxidation of hydroquinone. Kinetic parameters calculated from Lineweaver-Burke plots were observed to be K-m = 8 X 10(-5) and V-max = 1.53 for free enzyme, and K-m = 8.3 X 10(-5) and V-max = 2.18 for entrapped enzyme when enzyme concentration was kept constant and K-m = 4 X 10(-11) and V-max = 0.45 for free enzyme and K-m = 4.5 X 10(-11) and V-max = 0.58 for entrapped enzyme when substrate concentration was kept constant. This indicates that there is no conformational change during entrapment. (C) 2003 Wiley Periodicals, Inc.