Well-oriented bioarchitecture for immobilization of chloroperoxidase on graphene oxide nanosheets by site-specific interactions and its catalytic performance

Abstract

Chloroperoxidase (CPO) was immobilized on graphene oxide (GO) nanosheets via site-specific interactions of concanavalin (ConA) with saccharide groups on the CPO surface to make GO-ConA-CPO nano-architectonics. Enzymatic oxidative decolorization of malachite green was used to investigate the catalytic performance of GO-ConA-CPO. The GO-ConA-CPO showed high activity (based on the decolorization efficiency), i.e., 93.68% in 15 min. Moreover, GO-ConA-CPO showed better thermostability and remained higher activity against pH change and high concentrations of oxidant H2O2 compared with GO-CPO and the free enzyme. When incubated at 60 °C for 1.5 h, 63.02% of the activity of GO-ConA-CPO and 35.75% of GO-CPO remained compared with that at 25 °C, while free CPO remained only 8.46% in the same condition. The tolerance of GO-ConA-CPO to H2O2 improved from 2.5 to 6 mmol L−1, and the suitable pH range enlarged from 2.5–3.0 to 2.0–4.5. After 8 cycles, the GO-ConA-CPO can keep 52% activity of that in the first run. The enzymatic kinetic constants indicated that introducing CPO into GO-ConA-CPO bioarchitecture improved the diffusion of reactants and products.