Poly(p-maleimidostyrene) (PMS) was coated on cross-linked polystyrene(CLPS) beads. Enzymes (i.e., urease and fumarase) were stably immobilized on the beads via simple immersion into an enzyme solution for 30 min. Characterizations of PMS-coated on CLPS beads and evaluations of the enzymatic activity of bead-immobilized enzymes were conducted with confocal laser microscopy, electrochemical analysis, and spectro photometry. Immobilized urease and fumarase demonstrated satisfactory enzyme activities. The Km of immobilized urease was estimated using electrochemical measurements and was found to be 2.2 X 10(-3) M at 20 degrees C. PMS coating and immobilized enzymes both did not detach from the CLPS bead surface, even after ultrasonic irradiation. A biosensor using urease-immobilized. PMS-coated CLPS beads showed good performance as a urea sensor. Furthermore, fumarase-immobilized PMS-coated beads may be promising materials for bioreactors producing (S)-(-)-malic acid. (c) 2008 Elsevier Ltd. All rights reserved.