Understanding the Factors Influencing the Ability of Calcium-Binding Peptides to Promote Calcium Absorption

The objective of this research was to determine the factors that influence the ability of calcium-binding peptides, obtained through in silico enzymatic hydrolysis of whey proteins, to promote calcium absorption. Isothermal titration calorimetry and density functional theory calculations revealed that all of the investigated peptides could spontaneously bind calcium through an entropy-driven endothermic binding reaction via their terminal and side-chain carboxyl groups at physiological pH. Among the investigated peptides, tripeptide EAC demonstrated the strongest ability to promote calcium absorption, with a calcium ion activity-based binding constant of 209 L/mol and a promotion factor of 2.57. The ability of calcium-binding peptides to promote calcium absorption was not correlated with their calcium-binding constants but rather with their chemical hardness and ionization potential. Machine learning modeling of all 8400 dipeptides and tripeptides indicated that those with higher log P values and aliphatic N/C-termini or aromatic C-termini were more likely to effectively promote calcium absorption. These findings provide valuable insights for the design of peptides to increase calcium bioavailability.