Semi-preparative isolation of phosphopeptides derived from bovine casein and dephosphorylation of casein phosphopeptides

Identification of casein phosphopeptides released after simulated digestion of milk-based infant formulas

Adapted, follow-up, probiotic follow-up, toddler, and probiotic toddler infant formulas were subjected to an in vitro enzymatic procedure simulating physiological digestion. The formation and identification of casein phosphopeptides (CPPs) in the milk-based infant formulas were studied using reversed phase high-performance liquid chromatography coupled on line to an ion trap mass spectrometer. Most CPPs formed contained the cluster sequence SpSpSpEE, a mineral binding site. Phosphopeptide alpha(s2)-CN(1-19)4P was present in all formulas analyzed. Probiotic formulas released CPPs not detected in nonprobiotic formulas and probably formed by bifidobacteria action. These observations suggest that physiological digestion of these products promotes the formation of bioactive peptides with mineral carrier properties in the gastrointestinal tract, which resist further proteolysis.

Post-translational phosphorylation affects the IgE binding capacity of caseins

IgE response specific to those molecular regions of casein that contain a major phosphorylation site was analyzed using native and modified caseins and derived peptides. This study included (i) the naturally occurring common variants A1 and A from beta- and alphas2-caseins, respectively, which were purified in the native form and then dephosphorylated, (ii) a purified rare variant D of alphas2-casein which lacks one major phosphorylation site, and (iii) the native and dephosphorylated tryptic fragment f(1-25) from beta-casein. Direct and indirect ELISA using sera from patients allergic to milk showed that the IgE response to caseins is affected by modifying or eliminating the major phosphorylation site.