Zinc bioavailability from whey. Enthalpy-entropy compensation in protein binding. (November 2016)

• Record Type: Journal Article
• Authors: Tang, Ning; Skibsted, Leif H.
• Is Part Of: Food research international. Volume 89(2016) Part 1
• Page Start: 749
• Page End: 755
• Publication Date: 2016-11
• Subjects: Zinc -- Whey proteins -- Isothermal titration calorimetry -- Enthalpy-entropy compensation; Food -- Analysis -- Periodicals; Food industry and trade -- Periodicals; Food industry and trade -- Canada -- Periodicals; Food Technology -- Periodicals; Food -- Periodicals; Food-Processing Industry -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Industrie et commerce -- Canada -- Périodiques; Aliments -- Recherche -- Périodiques; Food industry and trade; Canada; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.foodres.2016.10.002
• Languages: English
• ISSNs: 0963-9969

Abstract

Abstract: Zinc amino acid or peptide complexes improve zinc absorption, however, the thermodynamics behind the interaction between zinc ion and these potential ligands is not well characterized. Therefore, binding of zinc to amino acids, peptides and whey proteins were investigated by isothermal titration calorimetry to provide useful information for improving zinc bioavailability which is lowered by many food components like phytate. Zinc binding to lactoferrin and to bovine serum albumin was found exothermic with ∆ H = − 100 kJ/mol and − 30 kJ/mol, respectively, in aqueous 0.16 M NaCl of pH 7.4 at 25 °C by isothermal titration calorimetry, while binding to α-lactalbumin and β-lactoglobulin was slightly endothermic. Still the binding constant was for all four proteins found to have a value around 2 × 10 5 L/mol indicating enthalpy-entropy compensation as also confirmed for zinc binding to amino acids with cysteine being enthalpically favored, while serine < histidine < glutamate < phosphorylated serine increasingly were found entropically favored. The enthalpy-entropy compensation makes whey proteins more homogeneous as zinc vehicles counteracting concentration fluctuation and precipitation of zinc. Graphical abstract: Highlights: Cysteine and histidine are the strongest zinc binding amino acids. Enthalpy entropy compensation makes zinc binding to whey proteins homogeneous. Zinc binding to lactoferrin and BSA is exothermic, to α-lactalbumin and β-lactoglobulin endothermic.