Cross-linked Enzyme Aggregates of Catalase from Bovine Liver

Stabilization of multimeric enzymes is one of the major challenges in biocatalysis, because dissociation of subunits can inactivate the enzyme. Catalase (CAT; EC 1.11.16) is a homotetramer containing Fe-protoporphyrin IX in its active site. CAT breaks down hydrogen peroxide into water and molecular oxygen. In this study, crosslinked enzyme aggregates of bovine liver CAT (CAT-CLEAs) were prepared. The effects of precipitation and cross-linking on enzyme activity were studied. Thermal stability of free and immobilized enzyme were also evaluated at 40 oC and pH 7 (200 h). CAT-CLEAs were successfully prepared using ammonium sulfate and glutaraldehyde (50 mM) as the precipitant and cross-linking agent, respectively. The best recovered activity obtained was 62 %. The derivative retained high activity along the stability test. The kinetic parameters values vmax and Km were estimated as 11,350 U/mg and 66.7±10 mM for the free CAT and 2,000 U/mg and 392±22 mM for the CAT-CLEAs, respectively.