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.

Structural aspects of legume proteins and nutraceutical properties

“…Structurally stable allergens are represented by proteins from pollen (e.g. birch), seeds (soybean, peanut, mustard, rice, wheat), fruit and vegetables (kiwi, grape, plums and celery) (Pauli, 2011), some examples being peanut trypsin inhibitor, soybean β-conglycinin, kiwi fruit actinidin and grape lipid transfer protein (Bublin et al, 2008;Vassilopoulou et al, 2006).…”

In Vivo Digestion of a Thaumatin-Like Kiwifruit Protein in Rats

“…An increase in pH of gastric fluid from 1.5 to 2.5 was recently shown to reduce pepsin breakdown of kiwifruit allergens significantly [21]. Both Act d 1 and Act d 2 survived longer when digested at pH 2 in vitro, which approximates physiological conditions [7]. Protein structure can also be influenced by pH, which modifies accessibility to cleavage sites, so contributing to changes in proteolysis patterns which may increase the risk of sensitization against food allergens [26].…”

In Vitro Gastric and Intestinal Digestions of Pulsed Light-Treated Shrimp Extracts

“…Digestion was performed in volumes of 1 mL. Aliquots of 200 μL were removed and terminated at 0, 5, 15, 60, and 120 min with trypsin inhibitor (Sigma) at a ratio of 1:1 (w/w, trypsin inhibitor to trypsin and chymotrypsin) as described by Bublin et al [22]. Three independent trials were conducted (n03).…”