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Stability of the major allergen Brazil nut 2S albumin (Ber e 1) to physiologically relevant in vitro gastrointestinal digestion
Author(s) -
Moreno F. Javier,
Mellon Fred A.,
Wickham Martin S. J.,
Bottrill Andrew R.,
Mills E. N. Clare
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2004.04472.x
Subject(s) - digestion (alchemy) , albumin , bovine serum albumin , chemistry , proteolysis , allergen , pepsin , biochemistry , epitope , protein subunit , microbiology and biotechnology , chromatography , biology , antibody , immunology , allergy , enzyme , gene
The major 2S albumin allergen from Brazil nuts, Ber e 1, was subjected to gastrointestinal digestion using a physiologically relevant in vitro model system either before or after heating (100 °C for 20 min). Whilst the albumin was cleaved into peptides, these were held together in a much larger structure even when digested by using a simulated phase 1 (gastric) followed by a phase 2 (duodenal) digestion system. Neither prior heating of Ber e 1 nor the presence of the physiological surfactant phosphatidylcholine affected the pattern of proteolysis. After 2 h of gastric digestion, ≈ 25% of the allergen remained intact, ≈ 50% corresponded to a large fragment of M r 6400, and the remainder comprised smaller peptides. During duodenal digestion, residual intact 2S albumin disappeared quickly, but a modified form of the ‘large fragment’ remained, even after 2 h of digestion, with a mass of ≈ 5000 Da. The ‘large fragment’ comprised several smaller peptides that were identified, by using different MS techniques, as deriving from the large subunit. In particular, sequences corresponding to the hypervariable region (Q37–M47) and to another peptide (P42–P69), spanning the main immunoglobulin E epitope region of 2S albumin allergens, were found to be largely intact following phase 1 (gastric) digestion. They also contained previously identified putative T‐cell epitopes. These findings indicate that the characteristic conserved skeleton of cysteine residues of 2S albumin family and, particularly, the intrachain disulphide bond pattern of the large subunit, play a critical role in holding the core protein structure together even after extensive proteolysis, and the resulting structures still contain potentially active B‐ and T‐cell epitopes.