Release of Protein-Bound N-ε -(γ -glutamyl)-Lysine during Simulated Gastrointestinal Digestion

https://doi.org/10.17221/962-CJFSCitation:Hellwig M., Löbner J., Schneider A., Schwarzenbolz U., Henle T. (2009): Release of Protein-Bound N-ε -(γ -glutamyl)-Lysine during Simulated Gastrointestinal Digestion. Czech J. Food Sci., 27: S153-S155.
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N-ε -(γ -glutamyl)-lysine is a crosslinking amino acid formed in food mainly during treatment with microbial transglutaminase (mTG). The purpose of this study was to investigate to which amount isopeptides are detectable in a low-molecular weight peptide fraction after simulated gastrointestinal digestion. Casein, which had been enriched with N-ε -(γ-glutamyl)-lysine by mTG to different extents, was subjected to simulated gastrointestinal digestion and the resulting peptide mixture fractionated into a low- and a high molecular weight fraction (below or above 200–500 Da, respectively) using semipreparative gel permeation chromatography. N-ε -(γ-glutamyl)-lysine was analysed in these fractions by RP-HPLC after enzymatic hydrolysis and derivatisation with phenyl isothiocyanate. N-ε -(γ-glutamyl)-lysine was found nearly exclusively in the high-molecular weight fraction, indicating that dietary N-ε -(γ-glutamyl)-lysine present in mTG-modified food proteins is not available for absorption in the intestine.
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