Influence of the presence of NaY zeolite on the activity of horseradish peroxidase in the oxidation of phenol

In this work a new enzyme–zeolite interaction was examined. Horseradish peroxidase (HRP-C), a heme-containing enzyme, shows an activity increase for HRP-C catalysed phenol and 4-aminoantipyrine co-oxidation in aqueous medium, in the presence of NaY zeolite, although the attempts to use this enzyme immobilized on the zeolite resulted in an almost complete loss of activity. -homogeneous mechanical mixtures of enzyme and zeolite in solution were compared at five different temperatures (10, 20, 25, 30 and 35 °C), and have shown possible interactions which influence the enzyme activity. In order to better analyse the interactions effects, co-immobilization of the enzyme and zeolite was performed in gelatin particles; in this case the enhancement in enzymatic activity was much larger than when pseudo-homogeneous mixtures were used. HRP-C immobilized in gelatin showed activity increases as large as 100% when zeolite NaY is co-immobilized in the same particles, depending on the experimental conditions. gh the mechanism by which the zeolite induces this effect still requires clarification, one possible explanation is that some ionization of OH groups of the enzyme occurs, due to ion exchange of Na-ions of the zeolite and protons of the enzyme, an effect which might also occur in the gelatin matrix; the zeolite may also influence the conformation of the enzyme by means of the electrical fields that are generated at the surface of these materials, which are known to influence the catalytic action of zeolites.