No abstract

In this study, a novel calcium-binding heptapeptide (NDEELNK) that is released during the trypsin hydrolysis of sea cucumber ovum was identified by peptidomics. The calcium binding mode, in vitro digestion profile and calcium absorption of the NDEELNK-calcium complex were investigated. The NDEELNK peptide could spontaneously bind calcium with a 1 : 1 stoichiometry, and the calcium-binding site might involve the carboxyl oxygen and amino nitrogen atoms of two glutamic acid and one aspartic acid residues in the NDEELNK peptide. The NDEELNK-calcium complex underwent disaggregation and self-aggregation in a mesh of smaller size during simulated gastrointestinal digestion, clarified by dynamic light scattering and confocal laser-scanning microscopy. In addition, the NDEELNK-calcium complex could be conducive to calcium absorption across Caco-2 cell monolayers. The findings from this research suggest possible utilization of hydrolyzed peptides from sea cucumber ovum as dietary supplements to improve calcium absorption.

Carboxyl oxygen and amino nitrogen atoms in the SCOHs could bind calcium ions, forming SCOH-calcium complexes. These complexes improved calcium solubility under simulated gastrointestinal digestion and also promoted calcium absorption in Caco-2 and HT-29 cells. © 2017 Society of Chemical Industry.

No abstract

In this study, the binding mechanism, morphological, and conformational analysis of the complex of a sea cucumber ovum derived octapeptide (EDLAALEK) with Ca2+ as well as its calcium delivery behavior via the gastrointestinal (GI) tract were investigated. The Ca2+ specifically bound to two carboxyl oxygen atoms of C-terminal Glu and Asp on the EDLAALEK peptide at a stoichiometric ratio of 1:1. Calcium coordination induced the self-assembly of the EDLAALEK peptide, resulting in the formation of a nanocomposite with a crystal structure. Furthermore, the formed nanocomposite went through dissociation and self-assembly during in vitro GI digestion, accompanied by the release and rechelation of Ca2+, which was related to changes in their secondary structure. Nevertheless, the GI digests of the EDLAALEK–calcium complex could significantly enhance Ca2+ absorption across Caco-2 cell monolayers. The findings suggest that the sea cucumber ovum derived peptide has the potential as an efficient nanocarrier to transport calcium through the GI system.