Probing of primed and unprimed sites of calpains: Design, synthesis and evaluation of epoxysuccinyl-peptide derivatives as selective inhibitors

• Published in: European journal of medicinal chemistry 2014-07, Vol.82, p.274-280
• Main Authors: Dókus, Levente E., Menyhárd, Dóra K., Tantos, Ágnes, Hudecz, Ferenc, Bánóczi, Zoltán
• Format: Article
• Language: English
• Subjects: Calpain; Calpain - antagonists & inhibitors; Calpain - metabolism; Cathepsin B - antagonists & inhibitors; Cathepsin B - metabolism; Dose-Response Relationship, Drug; Drug Design; Enzyme inhibitor; Epoxy Compounds - chemical synthesis; Epoxy Compounds - chemistry; Epoxy Compounds - pharmacology; Epoxysuccinic acid; Epoxysuccinyl-peptide; Humans; Models, Molecular; Molecular Conformation; Oligopeptides - chemical synthesis; Oligopeptides - chemistry; Oligopeptides - pharmacology; Protease Inhibitors - chemical synthesis; Protease Inhibitors - chemistry; Protease Inhibitors - pharmacology; Structure-Activity Relationship
• ISSN: 0223-5234; 1768-3254
• DOI: 10.1016/j.ejmech.2014.05.058

Calpains are intracellular cysteine proteases with important physiological functions. Up- or downregulation of their expression can be responsible for several diseases, therefore specific calpain inhibitors may be considered as promising candidates for drug discovery. In this paper we describe the synthesis and characterization of a new class of inhibitors derived from the analysis of amino acid preferences in primed and unprimed sites of calpains by incorporation of l- or d-epoxysuccinyl group (Eps). Amino acids for replacement were chosen by considering the substrate preference of calpain 1 and 2 enzymes. The compounds were characterized by RP-HPLC, amino acid analysis and ESI-MS. Selectivity of the compounds was studied by using calpain 1 and 2; and cathepsin B. We have identified five calpain specific inhibitors with different extent of selectivity. Two of these also exhibited isoform selectivity. Compound NH2-Thr-Pro-Leu-(d-Eps)-Thr-Pro-Pro-Pro-Ser-NH2 proved to be a calpain 2 enzyme inhibitor with at least 11.8-fold selectivity, while compound NH2-Thr-Pro-Leu-(l-Eps)-Ser-Pro-Pro-Pro-Ser-NH2 possesses calpain 1 enzyme inhibition with at least 4-fold selectivity. The results of molecular modeling calculations suggest that the orientation of the bound inhibitor in the substrate binding cleft is markedly dependent on the stereochemistry of the epoxysuccinyl group. [Display omitted] •Synthesis of novel calpain substrate based trans-epoxysuccinyl-peptide inhibitors.•Insertion of trans-epoxysuccinyl group into sequence resulted in inhibitor molecule.•Amino acids at P4–P5′ positions determined the enzyme inhibition.•Stereochemistry of trans-epoxysuccinyl group is important on the inhibitory activity.