ALPHA-AMYLASE IMMOBILIZED ON PLASTIC SUPPORTS - STABILITIES, PH AND TEMPERATURE PROFILES AND KINETIC-PARAMETERS

The covalent immobilization of alpha-amylase on new isocyanate, acid c hloride and carboxylic acid - activated plastic supports shows the via bility of such supports for immobilizing enzymes, specially those reac ting with 1,6-diaminohexane and glutaraldehyde for producing side arms . The operational stability of immobilized alpha-amylase could be exte nded by crosslinking the enzyme or by extending the support's side arm (substrate concentration has no effect). Inactive immobilized alpha-a mylase were unfolded and then refolded at elevated temperature, these supports were found to be essential in increasing the stability of the enzyme during refolding. The pH curves for the immobilized enzyme wer e in general found not to be shifted from the soluble enzyme's pH opti mum, although one isocyanate plastic support derivative shifted the pH activity profile of alpha-amylase to a higher range by 1.5 pH units, probably due to reaction between the enzyme and the free anhydride gro ups existing on the support's surface. In all cases, the immobilized e nzyme's temperature activity profiles were shifted to a lower temperat ure range when compared to the soluble enzyme. The immobilized alpha-a mylase Michaelis constants increased and the the maximum rates and spe cific activities decreased when compared to the soluble enzyme kinetic parameters.