A novel nanozyme based on selenopeptide-modified gold nanoparticles with a tunable glutathione peroxidase activity.

In this study, we successfully prepared a selenium-containing pentapeptide (Sec-Arg-Gly-Asp-Cys)-modified gold nanozyme that exhibited glutathione peroxidase (GPx) activity. The nanozyme catalyzed the reduction of HO by GSH, and its GPx activity was about 14 times that of free selenopeptide. Kinetic analysis indicated that the nanozyme changed the catalytic mechanism from the ping-pong mechanism of the peptide to an ordered mechanism. This indicated that the gold nanoparticle acts as a scaffold that may limit the mobility and constrain the conformation of the peptides, hence exposing the active center to the substrates, and allowing the multivalent selenopeptide to act cooperatively to increase the catalytic rate. Furthermore, upon addition of cysteamine to regulate the surface chemistry of gold nanoparticles and thereby modify the microenvironment of the active center, this nanozyme system could achieve a tunable GPx activity that was about 20 times that of free selenopeptide. Thus, the rational design of the nanozyme greatly improved and amplified the catalytic activity of the 'active unit' peptide. This study provides an alternative strategy to establish GPx mimics and provides new insights for the use of gold nanoparticles to develop nanozymes with biological applications.