Abstract
Recently, a number of simple oligopeptides have been developed as artificial enzymes for mimicking the activity and selectivity of natural hydrolases. Although the arrangement of amino acid residues in natural enzymes has been reported and their composition of active sites could provide a strategy for designing artificial enzymes, creating catalysts with both efficient binding and catalytic activity is still challenging. In this study, we designed a series of peptides with polyproline scaffold as artificial enzymes and also utilized the concept of catalytic dyad or triad and the co-assembly strategy. Their secondary structures were characterized by CD spectroscopy and their catalytic activities on ester hydrolysis were measured by UV-Vis spectroscopy using a series of p-nitrophenyl ester assay. In the first part, the results indicate that a well formed polyproline II (PPII) structure could result in a much higher catalytic efficiency. In addition, deprotonation steps in artificial enzymes are an important factor for obtaining a higher catalytic efficiency. In the second part, the results show that the triple helical stability of collagen-mimetic peptides could dramatically affect their catalytic efficiency. Furthermore, introducing zinc ions into collagen-mimetic peptides could mimic the active site in metalloenzymes and result in a higher catalytic efficiency. This is the first report of a functional dyad or triad engineered into a polyproline helix framework. Despite the fact that our designs are not as efficient as natural enzymes, the activity of our designs is still greater than some reported nanostructures. Our investigation has also revealed the necessity of maintaining a stable three-dimensional structure and a well-organized catalytic site for effective biocatalysts.