Identification of Novel Phosphopeptides After Simulated Digestion of αs2-casein by Tandem Mass Spectrometry

Abstract

Casein phosphopeptides (CPPs) are encrypted in α_s1-, α_s2-and β-casein (CN) and can be released by in vitro, in vivohydrolysis or food processing of dairy foods. Bovine α_s2-CN contains two cluster sequences of anionic phosphoseryl and glutamyl residues SpSpSpEE in its structure (residues 8–12 and 56–63), which can modulate mineral bioavailability. In this study α_s2-casein (α_s2-CN) was subjected to simulated gastrointestinal digestion. CPPs released were sequenced by on-line reversed-phase high performance liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (RP-HPLC-ESIMS/MS). Six novel α_s2-CN derived CPPs, Three of them (α_s2-CN(54–87)4P,α_s2-CN(24–70)4P and α_s2-CN(14–73)5P) with the mineral binding cluster sequence SpSpSpEE were identified and characterised. CPPs from α_s2-CN identified in this study resist simulated gastrointestinal digestion. As the molecular weights of these CPPs are approx. 2,165–7,112Da, they could be absorbed by intestinal cells. Consequently, these α_s2-CN derived CPPs could be promising candidates for incorporation to mineral fortified foods as functional ingredients.

Keywords

αs2-casein casein phosphopeptides mineral bioavailability identification

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