Peanuts, whose major allergen is Ara h 2, are included among the eight major food allergens. After reduction using dithiothreitol (DTT), cross-linking of Ara h 2 could be catalyzed by microbial transglutaminase (MTGase), a widely used enzyme in the food industry. In this study, Ara h 2 cross-linking was catalyzed by MTGase after it was reduced by DTT. Using mass spectrometry and PLINK software, five cross-linkers were identified, and five linear allergen epitopes were found to be involved in the reactions. The IgE binding capacity of cross-linked Ara h 2 was found to be significantly lower compared to that of native and reduced Ara h 2. After simulated gastric fluid (SGF) digestion, the digested products of the cross-linked Ara h 2, again, had a significantly lower IgE binding capacity compared to untreated and reduced Ara h 2. Furthermore, reduced and cross-linked Ara h 2 (RC-Ara h 2) induced lower sensitization in mice, indicating its lower allergenicity. Reduction and MTGase-catalyzed cross-linking are effective methods to decrease the allergenicity of Ara h 2. The reactions involved linear allergen epitopes destroying the material basis of the allergenicity, and this might develop a new direction for protein desensitization processes.
Peanut is ranked among the eight major food allergens. Ara h 2 is its major allergen, recognized by more than 90% of serum IgE from peanut-allergic patients. Cross-linking catalysed by microbial transglutaminase (MTGase) is proved to be feasible to decrease the allergenicity of Ara h 2. The crosslinking reaction occurred both interand intra-molecular could gain products with different molecular weights. In this study, after MTGase catalysed crosslinking, the products were separated into low molecular weight part of Ara h 2 (LP-Ara h 2) and high molecular weight part of Ara h 2 (HP-Ara h 2), and the structure, digestibility, IgG and IgE binding capability of each part were analysed. Compared with LP-Ara h 2, HP-Ara h 2 was found to have looser structure, higher digestion rate and corresponding lower immunogenicity. By controlling the reaction condition to get different products, the protein desensitization processes would get a better result.
Peanut (Arachis hypogaea) is listed among the eight major food allergens, in which Ara h 2 is the major allergen. The microbial transglutaminase (MTGase)‐catalyzed cross‐linking reaction reduces the allergenicity of Ara h 2. However, deamidation might occur and influence the cross‐linking reaction. In this work, native and reduced Ara h 2 were catalyzed by MTGase. In addition to intermolecular cross‐linking, intramolecular cross‐linking and deamidation were proven to occur simultaneously. Moreover, intramolecular cross‐linking sites were identified using mass spectrometry and the PLINK software. The reactions moved toward different directions because of different reduction conditions and different protein concentrations. Practical applications Cross‐linking is a common processing method used to improve the textural and functional properties of protein. Deamidation reaction might occur during processing and influence the cross‐linking reaction. The two types of reactions have a competitive relation, because both of them occur on glutamine residue. In Ara h 2 and MTGase system, protein concentration and reduction content influence the direction of reaction. The results can be applied to modify the reaction system of Ara h 2 catalyzed by MTGase. In addition, the relationship between structure and properties changes on Ara h 2 was discussed based on analysis of cross‐linking sites.
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