Visible-Light-Induced Effects of Au Nanoparticle on Laccase Catalytic Activity

A deep understanding of the interaction between the nanoparticle and enzyme is important for biocatalyst design. Here, we report the in situ synthesis of laccase-Au NP (laccase-Au) hybrids and its catalytic activity modulation by visible light. In the present hybrid system, the activity of laccase was significantly improved (increased by 91.2% vs free laccase) by Au NPs. With a short time visible light illumination (lambda>420 nm, within 3 min), the activity of laccase-Au hybrids decreased by 8.1% (vs laccase Au hybrid without light), which can be restored to its initial one when the illumination is removed. However, after a long time illumination (lambda > 420 nm, over 10 min), the catalytic activity of laccase Au hybrids consecutively decreases and is not reversible even after removing the illumination. Our experiments also suggested that the local surface plasma resonance effect of Au NPs causes the structure change of laccase and local high temperature near the Au NPs. Those changes eventually affect the transportation of electrons in laccase, which further results in the declined activity of laccase.