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] .