Inhibition of Dipeptidylpeptidase-IV by (2S)-Cyanopyrrolidine Inhibitors of Prolyl Endopeptidase

Objective: Prolyl endopeptidase (PEP) and dipeptidyl peptidase IV (DPP4) are serine peptidases, cleaving peptides at the carboxyl group of proline residues. These enzymes are involved in the regulation of many physiological processes, participating in the production, modification, and utilization of neuropeptides and peptide hormones. We found that compounds of the X-Y-2-S-cyanopyrrolidine general formula, where X is a protecting group and Y is any amino acid other than glycine and proline, which are PEP inhibitors, also inhibit DPP4. To explain the unexpected ability of these compounds to inhibit DPP4, we set out to develop a structurally reasoned insights of their interaction with the PEP and DPP4 active sites. Methods: To achieve this goal, we synthesized a series of N-protected amino acid derivatives of 2-S-cyanopyrrolidine, determined their inhibition constants for PEP and DPP4, and performed molecular dynamics modeling of the structures of these complexes. Results and Discussion: X-Y-2-S-pyrrolidine PEP inhibitors can inhibit DPP4, if X is a benzyloxycarbonyl or succinyl protecting group and Y is not a glycine or proline residue, i.e., they are L-amino acid residues with side chains. Among them, N-benzyloxycarbonylamino-L-methionyl-2S-pyrrolidine-2-carbonitrile has pronounced antiamnesic activity. Molecular dynamics modeling showed that the large hydrophobic side chain of methionine or tryptophan residues in the inhibitor ensures its binding to the active site of DPP4, compensating for steric hindrance created by the N-protecting group. Conclusions: Using molecular dynamics modeling methods, we established a relationship between the structure of 2-S-cyanopyrrolidine amino acid derivatives and their ability to inhibit DPP4. This opens the prospect of creating new drugs, affecting the peptidergic link in the regulation of functional systems in normal conditions and in various pathological processes.