Casein‐derived bioactive phosphopeptides: role of phosphorylation and primary structure in promoting calcium uptake by HT‐29 tumor cells

Abstract

Casein phosphopeptides L L-CN(1^25)4P and K K s1 -CN(59^79)5P, from L L-and K K s1 -casein, respectively, both carrying the characteristic 'acidic motif' Ser(P)-Ser(P)-Ser(P)-GluGlu, were chemically synthesized and administered to HT-29 cells di¡erentiated in culture, which are a used model of intestinal epithelium for absorption studies. Both casein phosphopeptides caused an increase of [Ca 2+ ] i due to in£ux of extracellular Ca 2+ . The response was quantitatively higher with L L-CN(12 5)4P than K K s1 -CN(59^79)5P. The synthetic peptide corresponding to the 'acidic motif' was ine¡ective and the dephosphorylated form of L L-CN(1^25)4P almost inactive. The lack of the N-terminally located ¢ve amino acids, or sequence modi¢-cations within the N-terminal segment of L L-CN(1^25)4P, caused a total loss of activity, whereas the lack of the C-terminal segment preserved activity. In conclusion, the in£ux of calcium into HT-29 cells caused by L L-CN(1^25)4P appears to depend on the phosphorylated 'acidic motif' and the preceding N-terminal region.

Biopeptides of milk: caseinophosphopeptides and mineral bioavailability

“…The phosphopeptides derived from α s caseins, more strongly phosphorylated, have a tendency to decrease the quantity of iron available biologically [15]. The superiority of β(1-25) as a vector as compared to the phosphopeptides of α s -casein has also been observed recently in the uptake of calcium by culture cells [7]. These results underline the importance of the physicochemical properties of these complexes on the expression of their biological activity.…”

“…Current studies on the role of phosphopeptides in the use of calcium are focused on a better consideration of the different factors affecting the bioavailability of calcium on the one hand and on the exploration of the mechanisms involved on the other hand. Concerning this latter point, a recent study has shown that the phosphorylated region as well as the N-terminal part are necessary for a positive effect of the phosphopeptides on the uptake of calcium by human cells in culture (HT-29) [7].…”

Bioactive Casein Phosphopeptides in Dairy Products as Nutraceuticals for Functional Foods

“…Ca could be bound to either SerP or Glu residues [61], suggesting that CPP may enhance the solubility of calcium in the intestinal lumen, thereby increasing the mineral availability for absorption in the small intestine [62,13]. Chemically synthesized CPP, i.e., -CN (f1-25)4P and s1-CN (f59-79)5P, carrying the characteristic cluster Ser(P)-Ser(P)-Ser(P)-Glu-Glu, increase the intracellular calcium uptake by the human cultured HT-29 tumor cells [63], Caco-2 cells [64] and osteoblasts [65]. A more pronounced effect has been observed for -CN-derived peptides than for s1-CN-counterparts.…”

“…A more pronounced effect has been observed for -CN-derived peptides than for s1-CN-counterparts. It has been suggested that CPP promote calcium binding, which would depend on the structural conformation conferred by the two phosphorylated 'acidic motif' and the N-terminal sequence of -CN [63].…”

A chromatographic procedure for semi-quantitative evaluation of caseinphosphopeptides in cheese

“…I), thus suggesting the action of phosphatases on phosphocaseins and their fragments during cheese ripening, but further studies are needed in this field [22]. However, the characteristic "acidic motif" Ser(P)-Ser(P)-Ser(P)-Glu-Glu is still carried by all the CPPs found in fraction V, making them potential candidates for having effects on calcium absorption [6].…”