The noncovalent immobilization of enzymes such as alpha-amylase, beta-glucosidase, trypsin, and alkaline phosphatase was performed by adsorption on the water-soluble polymer Eudragit S-100. The strength of the binding with enzymes in some cases was critically dependent upon the initial polymer concentration used during binding. In all the cases tried, a moderate increase in polymer concentration ensured adequate immobilization of enzymes. The immobilized enzymes retained different activities: 87, 59, 49, and 24% for beta-glucosidase. alpha-amylase, trypsin, and alkaline phosphatase, respectively. The K, value of immobilized enzyme was the
same as that of native enzyme for beta-glucosidase (3.8 x lo-’ M) and alpha-amylase (6 mg ml-‘) whereas the K, value decreased in the case of trypsin (from 1 x 10m3 M to 0.6 x lo-’ M) upon immobilization, The immobilized trypsin showed improved stability to autolysis at 35°C whereas immobilization resulted in a decrease
in the thermal stability of alpha-amylase at 5O’C. No significant changes were observed in pH optimum of the enzymes upon immobilization. U.V. and fluorescence emission spectra of immobilized trypsin reflected the con-formational changes which enzymes undergo upon adsorption on the polymer.