Polyacrylamide gels as support for enzyme immobilization by entrapment. Effect of polyelectrolyte carrier, pH and temperature on enzyme action and kinetics parameters

This study investigates the main interactions which occur among enzymes and the polymeric support in which they are immobilized, when charges are crea ted within the support as a result of the effect of external variables. The electrostatic held generated by the charges has a major impact on the enzy matic activity and kinetic parameters. In the most extreme conditions for t he external variables, the pH of the interior of the support is displaced b y 1.5 pH units towards more alkaline values. Measured at pH 10.0, the Micha elis constant for immobilized enzymes is 17 times higher than for free enzy mes. The displacement in the pH-activity profiles, pH of the interior of the sup port and the kinetic parameters is a consequence of the non-uniform distrib ution of the hydrogen ions and negatively charged substrate molecules betwe en the microenvironment of the enzyme and that of the solution. The theoret ical analysis of the electrostatic potential created by the charges of the support allows obtaining correlations to quantify the displacement of these parameters. (C) 2001 Elsevier Science Ltd. All rights reserved.