9 1995by Humana Press Inc. All rights of any nature whatsoeverreserved. 0273-228919515001--0011508.60 Investigations of Stabilities, pH, and Temperature Profiles and Kinetic Parameters of Glucoamylase Immobilized on Plastic Supports M. G. ROIG, 1 A. SLADE, 2 J. F. KENNEDY "'2 D. W. TAYLOR, 2 AND M. G. GARAITA 2 l Departamento de Quimica Fisica, Facultad de Farmacia, Universidad de Salamanca, Espaha; and 2Birmingham Carbohydrate and Technology Group, Research Laboratory for the Chemistry of Bioactive Carbohydrates and Proteins, School of Chemistry, Birmingham University, B15 2TT, UK Received June 29, 1993; Accepted March 10, 1994 ABSTRACT The covalent immobilization of glucoamylase on new epoxide-, isocyanate-, acid chloride-, and carboxylic acid-activated plastic sup- ports shows the viability of such supports for immobilizing enzymes (especially those reacting with 1,6-diaminohexane and glutaraldehyde) for producing side arms. The operational stability of immobilized glu- coamylase could be extended by crosslinking the enzyme, by increas- ing the substrate concentration, or by extending the support's side arm. The pH curves for the immobilized enzyme were in general not found to be shifted from the pH optimum of the soluble enzyme. However, the immobilized enzyme's temperature activity profiles were shifted to a lower temperature range when compared to the soluble enzyme. The immobilized glucoamylase Michaelis constants increased, and the maximum rates and specific activities decreased with respect to the soluble enzyme kinetic parameters. Index Entries: Stability; pH; temperature; activity; kinetic; enzyme; glucoamylase; immobilization; plastic supports. *Author to whom all correspondence and reprint requests should be addressed. Applied Biochemistry and Biotechnology 1 1 Vol. 50, 1995