Synthesis and Characterisation of Chickpea Peptides-Zinc Chelates Having ACE2 Inhibitory Activity

Abstract

Tryptic hydrolysates of protein fractions obtained by the Osborne method from chickpea (Cicer arietinum L.) seeds interacted with zinc ions and the results of chelation were monitored by the Energy Dispersive X-Ray (EDX) technique. The glutelin hydrolysate (GluHyd) reacted with zinc ions and depicted a relatively higher zinc content. For this reason, the zinc complex of the glutelin hydrolysate (GluHyd-Zn) was studied deeper, and 11 peptides were identified in its more zinc-containing second fraction obtained after gel filtration. The peptide HKERVQLHIIPTAVGK showed a relatively higher chelating capacity (57.86 ± 2.14%). According to the result of the ICP-OS analysis, 1 mg peptide could chelate 381.61 ± 133.39 µg zinc, and the molar ratio of peptide-zinc was about 1:4. Spectral methods proved that side chain and C-termini carboxyl groups of the peptide mostly were involved in chelation and N atoms of amino side chains, imidazole group of histidine, and N-termini at some extents were occupied by the metal ions. Modeling of zinc-peptide interaction was done using Molecular Operating Environment (MOE) software. The results of the docking correlate with the experimental data.ACE2 inhibitory effect of HKERVQLHIIPTAVGK-Zn complex (IC₅₀ = 1.5 mg/mL) was better than that of HKERVQLHIIPTAVGK (IC₅₀ = 2.2 mg/mL).

Keywords: ACE2; Chickpea; Peptides; Zinc; Zinc-binding; Zinc-peptide complex.