Catalytic Pathway of Nanozyme “Artificial Peroxidase” with 100-Fold Greater Bimolecular Rate Constants Compared to Those of the Enzyme

Abstract

We report on the kinetic mechanism of the catalytically synthesized Prussian Blue nanoparticles denoted as "artificial peroxidase". In contrast to the enzyme, whose active site first interacts with hydrogen peroxide forming the so-called Compound I, in the case of the nanozymes, H2O2 oxidizes their complex with reducing substrate. Slow release of the product (oxidized form of the latter) from the nanozymes has been registered. The interaction of substrates with the nanozymes is 100 times faster than with enzyme peroxidases, and the rate-limiting constant for the nanozymes is also 2 orders of magnitude greater: for pyrogallol k2 = 1.3 ± 0.1 × 108 M-1 s-1 and for ferrocyanide k2 = 1.9 ± 0.1 × 108 M-1 s-1. Thus, the discovered novel advantage of nanozymes over the corresponding enzymes is the 100-fold greater bimolecular rate constants, resulting, most probably, from their uniformly accessible surface, avoiding the effect of rotation on the diffusion-controlled rate.