NONCOVALENT IMMOBILIZATION OF ENZYMES ON AN ENTERIC POLYMER EUDRAGIT S-100

The noncovalent immobilization of enzymes such as alpha-amylase, beta- glucosidase, trypsin, and alkaline phosphatase was performed by adsorp tion on the water-soluble polymer Eudragit S-100. The strength of the binding with enzymes in some cases was critically dependent upon the i nitial polymer concentration used during binding. In all the cases tri ed, a moder-ate increase in polymer concentration ensured adequate imm obilization of enzymes. The immobilized enzymes retained different act ivities: 87, 59, 49, and 24% for beta-glucosidase, alpha-amylase, tryp sin, and alkaline phosphatase, respectively. The K-m value of immobili zed enzyme was the same as that of native enzyme for beta-glucosidase (3.8 x 10(-3) M) and alpha-amylase (6 mg ml(-1)) whereas the K, value decreased in the case of trypsin (from 1 x 10(-3) M to 0.6 x 10(-3) M) upon immobilization. The immobilized trypsin showed improved stabilit y to autolysis at 35 degrees C whereas immobilization resulted in a de crease in the thermal stability of alpha-amylase at 50 degrees C. No s ignificant changes were observed in pH optimum of the enzymes upon imm obilization. U.V. and fluorescence emission spectra of immobilized try psin reflected the conformational changes which enzymes undergo upon a dsorption on the polymer. (C) 1997 by Elsevier Science Inc.