A novel polymeric phosphine oxide-derived support for enzyme immobilization was synthesized by Mannich condensation of P(CH2OH)(3) with a polyetheramine. The high-surface-area particles were smooth at high magnification and resisted adsorption of protein. Urease was linked to the support by glutaraldehyde coupling onto the polyetheramine, a flexible side chain. The properties of both the immobilized and free urease were compared. Upon immobilization, K-m(app) was increased by three-fold. The pH optimum was decreased by 0.5 pH units, whereas the temperature optimum was increased by 10 degrees C. Thermal stability remained approximately constant, but storage stability at 4 degrees C was increased by at least 5 weeks.