Insight into the Mechanism Underlying the Reduction of Digestibility and IgG/IgE Binding Ability in Ovalbumin during Different High-Temperature Conduction Modes-Induced Glycation.

Effects of different high-temperature conduction modes [high-temperature air conduction (HAC), high-temperature contact conduction (HCC), high-temperature steam conduction (HSC)]-induced glycation on the digestibility and IgG/IgE-binding ability of ovalbumin (OVA) were studied and the mechanisms were investigated. The conformation in OVA-HSC showed minimal structural changes based on circular dichroism, fluorescence, and ultraviolet spectroscopy. The degree of hydrolysis analysis indicated that glycated OVA was more resistant to digestive enzymes. Liquid chromatography-Orbitrap mass spectrometry identified 11, 14, and 15 glycation sites in OVA-HAC, OVA-HCC, and OVA-HSC, respectively. The IgG/IgE-binding ability of OVA was reduced during glycation and digestion, and the interactions among glycation, allergenicity, and digestibility were further investigated. Glycation sites masked the IgG/IgE epitopes resulting in a reduction in allergenicity. Digestion enzymes destroyed the IgG/IgE epitopes thus reducing allergenicity. Meanwhile, the glycation site in proximity to the digestion site of pepsin was observed to cause a reduction in digestibility.

Insights into the Mechanism Underlying the Influence of Glycation with Different Saccharides and Temperatures on the IgG/IgE Binding Ability, Immunodetection, In Vitro Digestibility of Shrimp (Litopenaeus vannamei) Tropomyosin.

Tropomyosin (TM) is a heat-stable protein that plays a crucial role as a major pan-allergen in crustacean shellfish. Despite the high thermal stability of the TM structure, its IgG/IgE binding ability, immunodetection, and in vitro digestibility can be negatively influenced by glycation during food processing, and the underlying mechanism remains unclear. In this study, TM was subjected to glycosylation using various sugars and temperatures. The resulting effects on IgG/IgE-binding capacity, immunodetection, and in vitro digestibility were analyzed, meanwhile, the structural alterations and modifications using spectroscopic and LC-MS/MS analysis were determined. Obtained results suggested that the IgG/IgE binding capacity of glycosylated TM, immunodetection recovery, and in vitro digestibility were significantly reduced depending on the degree of glycosylation, with the greatest reduction occurring in Rib-TM. These changes may be attributable to structural alterations and modifications that occur during glycosylation processing, which could mask or shield antigenic epitopes of TM (E3: 61-81, E5b: 142-162, and E5c: 157-183), subsequently reducing the immunodetection recognition and digestive enzyme degradation. Overall, these findings shed light on the detrimental impact of glycation on TMs potential allergenicity and digestibility immunodetection and provide insights into the structural changes and modifications induced by thermal processing.

Investigation of the Mechanism of 60Co Gamma-Ray Irradiation-Stimulated Oxidation Enhancing the Antigenicity of Ovalbumin by High-Resolution Mass Spectrometry.

60Co gamma-ray irradiation-induced antigenicity changes in ovalbumin (OVA) were investigated, and the molecular mechanism was analyzed. Irradiation treatment at 0-100 kGy could significantly enhance the IgG/IgE binding ability of OVA in a dose-dependent paradigm by concomitant oxidative modification, which exhibited color browning and an increase in carbonyl content caused by high-penetrable rays. More allergenic epitopes of OVA were exposed after irradiation treatment reflected by structural changes including the unfolding of tertiary structure, the conversion of α-helix structures to ß-sheet and random coil structures, and the cleavage of several peptide bonds. Meanwhile, three oxidation sites of K46, T49, and N260 located in key linear epitopes were observed, which might increase the allergenic ability of OVA via the disaggregation of noncovalent bonds and the unwinding of α-helix structures. Conclusively, irradiation may enhance the potential allergenicity of OVA by oxidative modification, which provides theoretical guidance for effectively controlling the oxidation of proteins in the irradiation process.

Analysis of the Structure and Antigenicity in Ovalbumin Modified with Six Disaccharides Through Liquid Chromatography-High-Resolution Mass Spectrometry.

Melibiose, cellobiose, maltose, lactose, turanose, and isomaltulose were selected to be glycated with OVA. The number of free amino groups of OVA modified with different disaccharides decreased, and the secondary and tertiary structures of the modified OVA also changed greatly. Moreover, the glycation sites detected by HPLC-HCD-MS/MS were all on the sensitized epitopes of OVA, which reduced the binding ability of IgG and IgE of glycated OVA. In addition, the glycation sites with the highest DSP in different samples were located in the irregular coil region of OVA. Among the six disaccharides, the glycation reaction between melibiose and OVA was the most obvious. Through the analysis of disaccharide configuration, it was found that the glycation efficiency of the reducing disaccharide linked by a 1 → 6 glycoside bond was higher than that by a 1 → 4 glycoside bond, and reducing sugar with ß type was better than that with α type. These findings would provide a theoretical reference for the use of different sugars in food production.

Insight into IgG/IgE binding ability, in vitro digestibility and structural changes of shrimp (Litopenaeus vannamei) soluble extracts with thermal processing.

The effects of six kinds of thermal processing on soluble protein recovery, potential allergenicity, in vitro digestibility and structural characteristics of shrimp soluble proteins were evaluated. Obtained results confirmed soluble protein recovery and IgG/IgE reactivity of shrimp soluble extracts were markedly suppressed by various thermal treatments with enhanced digestibility depended on the extent and type of heating applied, which correlated well with the structural alterations and modification. The maximum reduction of IgG/IgE-binding capacity and digestive stability were observed in the autoclaved shrimps because of unfolding of protein and hydrophobic residues exposed. Notably, tropomyosin (TM) and sarcoplasmic calcium-binding protein (SCP) were still IgG/IgE-reactive in various heat-processed shrimps, even higher IgG reactivity were found in heat-treated shrimps TM according to TM antiserum western-blotting and indirect ELISA results. Shrimp TM and SCP maintains its IgE/IgG-binding capacity after various cooking methods, thus most probably initiating allergic sensitization to both raw and cooked shrimps.

Mechanism of the effect of 2, 2'-azobis (2-amidinopropane) dihydrochloride simulated lipid oxidation on the IgG/IgE binding ability of ovalbumin.

In this work, the mechanism of the effect of lipid oxidation on the IgG/IgE binding ability of ovalbumin (OVA) was investigated via the peroxyl radicals produced by 2, 2'-azobis (2-amidinopropane) dihydrochloride to simulate lipid oxidation. Results showed that the structure of OVA unfolded partially with an increase in oxidation degree, leading to the exposure of the allergenic epitopes and increasing the IgG/IgE binding ability of OVA. Nine oxidation sites were found on the α-helix, and these sites may unwind the α-helix and expose the allergenic epitopes on the OVA surface, leading to antibody recognition and combination. Consequently, the IgG/IgE binding ability of OVA was increased. In conclusion, the allergenic capacity of OVA can be promoted by modifying peroxyl radical oxidation in processing egg products.