Identification of peptides from soybean protein, glycinin, possessing suppression of intracellular Ca²⁺ concentration in vascular smooth muscle cells

In this study, we challenged to identify vasoactive peptides in soybean 11S glycinin hydrolysate by thermolysin to regulate intracellular Ca²⁺ concentration ([Ca²⁺]_i) that can induce constrictive vascular tension. As a function of the inhibition of elevated [Ca ²⁺]_i by 10 μM angiotensin (Ang) II in vascular smooth muscle cells (VSMCs), eleven peptides were successfully identified from the hydrolysate, among which His-Gly-Lys exhibited the most potent inhibition against [Ca²⁺]_i elevation in Ang II-stimulated VSMCs (inhibition at 300 μM: 46.5 ± 8.0% vs. control). The biological capacity of His-Gly-Lys analogues as an [Ca²⁺]_i inhibitor was also proven when His-Lys and His-Gly-Arg elicited a significant reduction in [Ca²⁺]_i. In contrast, less reduction of [Ca ²⁺]_i by His-Gly-Ile and His-(3-methyl)-Gly-Lys indicated the importance of the imino proton in His, along with basic amino acids positioned at C-terminal for the effect.