Immobilization of Lactoperoxidase on Graphene Oxide Nanosheets and Copper Oxide Nanoparticles and Evaluation of Their Stability

Abstract

Lactoperoxidase (LPO) is a peroxidase enzyme that functions as a natural antibacterial, antiviral, antioxidant and antitumor agent. Stabilization of LPO is a key factor in its industrial applications. In this respect, this work focused on immobilizing LPO on graphene oxide (GO) nanosheets and copper oxide (CuO) nanoparticles using glutaraldehyde, as a cross-linking reagent, and investigating its stability. The Km values of free LPO and LPO immobilized on GO (LPO-GO) and CuO (LPO-CuO) were found to be 53.19, 83.33 and 98.7mM and their Vmax values equaled to 0.629, 0.504 and 0.41U/mL min, respectively. The LPO-GO and LPO-CuO samples retained 35 and 12 of their primary activity within 30 days at 25 degrees C whereas the free enzyme lost its activity after 7 days at the same temperature. Moreover, evaluation of the thermal stability of LPO at 75 degrees C determined conservation of 24 and 8 of the primary activity of LPO in the LPO-GO and LPO-CuO samples, respectively, after 60min whereas the free enzyme lost its activity after 5min. As the findings demonstrated, GO nanosheets are more appropriate for immobilization of LPO, compared with CuO. GRAPHICS .