Effect of Mini-PEGs Modification on the Enzymatic Digestion of D-Amino Acid-Containing Peptides under the Action of PROK**

Graphical A series of mini-PEGs modified D-amino acid-containing peptides were synthesized. It was determined that the polyethylene glycol (PEG) modification promoted the enzymatic cleavage of the D-amino acid-containing peptides under the action of serine-like proteases. It was previously reported that D-amino acid-containing peptides exhibited the ability to resist enzymatic hydrolysis. This study investigated the influence of mini-PEGs modification on enzymatic hydrolysis ability of D-amino acid-containing peptides. The results showed that PEGylation promoted enzymatic hydrolysis of the D-amino acid-containing peptide, especially, the cleavage rate of the D-amino acid-containing peptide 6-w with PEG 3 modification at the N-ends was up to 17 times higher in the presence of proteinase K (PROK) compared to those without PEG 3 modification. Moreover, analysis of the enzymatic cleavage sites demonstrated a similar cleavage pattern of the PEGylated D-amino acid-containing peptide to that of the unmodified peptide. The computational simulations further showed that the enhanced enzymatic hydrolysis ability can be attributed to the strong interaction between PROK and the peptide after PEG 3 modification and the resulting formation of a mature catalytic triad structure.