title: Effects of gastrointestinal digestion and heating on the allergenicity of the kiwi allergens Act d 1, actinidin, and Act d 2, a thaumatin-like protein.
abstract: Kiwifruit is a significant elicitor of allergy both in children and adults. Digestibility of two kiwifruit allergens, actinidin (Act d 1) and thaumatin-like protein (Act d 2), was assessed using an in vitro digestion system that approximates physiological conditions with respect to the passage of food through the stomach into the duodenum. Act d 1 precipitated in simulated gastric fluid at pH 2 and digestion of the aggregated protein proceeded slowly. The residual precipitate redissolved completely in simulated duodenal fluid at pH 6.5 and was partially digested. Forty percent of Act d 2 remained intact during gastric digestion and were cleaved by duodenal proteases into large fragments covalently linked by disulfide bonds. Both digested allergen samples displayed nearly unchanged IgE binding abilities. Circular dichroism spectra were used to analyze heat and acid-induced unfolding. Thermal stability of both allergens was strongly pH dependent. While Act d 1 was irreversibly destabilized in acidic solutions, heat-induced denaturation of Act d 2 at pH 2 was fully reversible. IgE binding to Act d 2 but not Act d 1 was detected in processed food products. The stability of Act d 1 and Act d 2 provides one explanation for the allergenic potency of kiwifruit.
authors.affiliation: Department of Pathophysiology, Medical University of Vienna, Vienna, Austria.
authors.forename: Merima
authors.initials: M
authors.lastname: Bublin
authors.forename: Christian
authors.initials: C
authors.lastname: Radauer
authors.forename: André
authors.initials: A
authors.lastname: Knulst
authors.forename: Stefan
authors.initials: S
authors.lastname: Wagner
authors.forename: Otto
authors.initials: O
authors.lastname: Scheiner
authors.forename: Alan R
authors.initials: AR
authors.lastname: Mackie
authors.forename: E N Clare
authors.initials: EN
authors.lastname: Mills
authors.forename: Heimo
authors.initials: H
authors.lastname: Breiteneder
mesh_terms: D029042:Actinidia / Q000009:adverse effects* / Q000737:chemistry / Q000276:immunology; D000485:Allergens / Q000276:immunology / Q000378:metabolism*; D052179:Antigens, Plant / Q000276:immunology / Q000378:metabolism*; D002942:Circular Dichroism; D003546:Cysteine Endopeptidases / Q000276:immunology / Q000378:metabolism*; D004063:Digestion; D005512:Food Hypersensitivity / Q000276:immunology / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; C003427:thaumatin protein, plant; D003546:Cysteine Endopeptidases; C018745:actinidain