Casein phosphopeptide promotion of calcium uptake in HT-29 cells - relationship between biological activity and supramolecular structure
2007
Gravaghi, Claudia | Del Favero, Elena | Cantú, Laura | Donetti, Elena | Bedoni, Marzia | Fiorilli, Amelia | Tettamanti, Guido | Ferraretto, Anita
Casein phosphopeptides (CPPs) form aggregated complexes with calcium phosphate and induce Ca²⁺ influx into HT-29 cells that have been shown to be differentiated in culture. The relationship between the aggregation of CPPs assessed by laser light scattering and their biological effect was studied using the CPPs β-CN(1-25)4P and αs₁-CN(59-79)5P, the commercial mixture CPP DMV, the 'cluster sequence' pentapeptide, typical of CPPs, and dephosphorylated β-CN(1-25)4P, [β-CN(1-25)0P]. The biological effect was found to be: (a) maximal with β-CN(1-25)4P and null with the 'cluster sequence'; (b) independent of the presence of inorganic phosphate; and (c) maximal at 4 mmol·L⁻¹ Ca²⁺. The aggregation of CPP had the following features: (a) rapid occurrence; (b) maximal aggregation by β-CN(1-25)4P with aggregates of 60 nm hydrodynamic radius; (c) need for the concomitant presence of Ca²⁺ and CPP for optimal aggregation; (d) lower aggregation in Ca²⁺-free Krebs/Ringer/Hepes; (e) formation of bigger aggregates (150 nm radius) with β-CN(1-25)0P. With both β-CN(1-25)4P and CPP DMV, the maximum biological activity and degree of aggregation were reached at 4 mmol·L⁻¹ Ca²⁺.
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