Preparation of an immobilized–stabilized catalase derivative from Aspergillus niger having its multimeric structure stabilized: The effect of Zn 2+ on enzyme stability

Abstract

Multimeric catalase from Aspergillus niger was immobilized on CNBr activated agarose, increasing the enzyme stability. However, it was found that some enzyme subunits could be desorbed to the supernatant after boiling the enzyme preparation in the presence of SDS or during thermal inactivation. Moreover, a positive enzyme concentration-enzyme stability correlation was detected in the immobilized preparation. This suggested the existence of some dissociation mechanism as a first step in the enzyme inactivation. The treatment of the immobilized enzyme with aldehyde–dextran permitted to fully stabilize its multimeric structure, but even this preparation exhibited an enzyme concentration-stability correlation. The presence of EDTA reduced the enzyme stability, suggesting that some cation could be involved in enzyme stability. It was found that 10 mM Zn 2+ increased the enzyme stability of this immobilized–stabilized preparation. Now, the dilution of the biocatalyst did not produce a reduction in the enzyme stability. Thus, we have prepared an immobilized enzyme that does not release any subunit to the medium even after inactivation, and found that Zn 2+ has a very positive effect on the stability of this immobilized–stabilized enzyme.