Enthalpy-entropy compensation in calcium binding to acid-base forms of glycine tyrosine dipeptides from hydrolysis of α-lactalbumin
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Enthalpy-entropy compensation in calcium binding to acid-base forms of glycine tyrosine dipeptides from hydrolysis of α-lactalbumin. / Jiang, Yuan; Liu, Xiao-Chen; Ahrné, Lilia M.; Skibsted, Leif H.
In: Food Research International, Vol. 149, 110714, 2021.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Enthalpy-entropy compensation in calcium binding to acid-base forms of glycine tyrosine dipeptides from hydrolysis of α-lactalbumin
AU - Jiang, Yuan
AU - Liu, Xiao-Chen
AU - Ahrné, Lilia M.
AU - Skibsted, Leif H.
N1 - Publisher Copyright: © 2021 The Author(s)
PY - 2021
Y1 - 2021
N2 - Calcium binding to peptides formed by hydrolysis of whey proteins during digestion is important for calcium uptake in the intestines and affects the antioxidant function of the peptides. For the two dipeptides, Gly-Tyr and Tyr-Gly, potential hydrolysis products of α-lactalbumin, calcium binding to the three forms of each dipeptide in acid-base equilibrium at intestinal pH was determined electrochemically and compared to binding to tyrosine for aqueous 0.16 M NaCl for 5 < pH < 9 at 15 °C, 25 °C, and 37 °C. At milk pH at 25 °C, binding of calcium to the zwitterion of GlyTyr dominates, with an association constant Kass2 = 22 M−1 with ΔH0 = −46 kJ·mol−1, while binding to the mononegative TyrGly dominates for TyrGly with Kass3 = 32 M−1 and ΔH0 = −38 kJ·mol−1. At intestinal conditions, pH = 7 and 37 °C, binding of calcium has similar affinity for GlyTyr and TyrGly, while at higher pH and lower temperature, GlyTyr binds stronger. Density Functional Theory calculations confirmed a stronger binding to the zwitterion of GlyTyr than of TyrGly and an increasing affinity with increasing pH for both. Calcium binding to the acid/base forms of the dipeptides is at neutral pH strongly exothermic with ΔH0 becoming less negative at higher pH, and a linear enthalpy–entropy compensation (r2 = 0.99) results in comparable binding important for calcium bioavailability along the changing distribution among acid-base forms. Calcium binding decreases radical scavenging rate and antioxidative activity of both dipeptides.
AB - Calcium binding to peptides formed by hydrolysis of whey proteins during digestion is important for calcium uptake in the intestines and affects the antioxidant function of the peptides. For the two dipeptides, Gly-Tyr and Tyr-Gly, potential hydrolysis products of α-lactalbumin, calcium binding to the three forms of each dipeptide in acid-base equilibrium at intestinal pH was determined electrochemically and compared to binding to tyrosine for aqueous 0.16 M NaCl for 5 < pH < 9 at 15 °C, 25 °C, and 37 °C. At milk pH at 25 °C, binding of calcium to the zwitterion of GlyTyr dominates, with an association constant Kass2 = 22 M−1 with ΔH0 = −46 kJ·mol−1, while binding to the mononegative TyrGly dominates for TyrGly with Kass3 = 32 M−1 and ΔH0 = −38 kJ·mol−1. At intestinal conditions, pH = 7 and 37 °C, binding of calcium has similar affinity for GlyTyr and TyrGly, while at higher pH and lower temperature, GlyTyr binds stronger. Density Functional Theory calculations confirmed a stronger binding to the zwitterion of GlyTyr than of TyrGly and an increasing affinity with increasing pH for both. Calcium binding to the acid/base forms of the dipeptides is at neutral pH strongly exothermic with ΔH0 becoming less negative at higher pH, and a linear enthalpy–entropy compensation (r2 = 0.99) results in comparable binding important for calcium bioavailability along the changing distribution among acid-base forms. Calcium binding decreases radical scavenging rate and antioxidative activity of both dipeptides.
KW - Calcium binding
KW - Calcium bioavailability
KW - Density Functional Theory
KW - Dipeptide
KW - Enthalpy–entropy compensation
U2 - 10.1016/j.foodres.2021.110714
DO - 10.1016/j.foodres.2021.110714
M3 - Journal article
C2 - 34600648
AN - SCOPUS:85115090201
VL - 149
JO - Food Research International
JF - Food Research International
SN - 0963-9969
M1 - 110714
ER -
ID: 281158635