Effect of tyrosinase-aided crosslinking on the IgE binding potential and conformational structure of shrimp ( Metapenaeus ensis ) tropomyosin

Effect of different pretreatment methods on the stability of pumpkin seed milk and potential mechanism

Pumpkin seeds represent a valuable source of plant protein and can be utilized in the production of plant-based milks. This study aims to investigate the effects of different pretreatment techniques on the stability of Pumpkin Seed Milk (PSM) and explore potential mechanisms. Raw pumpkin seeds underwent pretreatment through roasting, microwaving, and steaming to prepare PSM. Physiochemical attributes such as composition, storage stability, and particle size of PSM were evaluated. Results indicate that stability significantly improved at roasting temperatures of 160 °C, with the smallest particle size (305 ± 40 nm) and highest stability coefficient (0.710 ± 0.002) observed. Nutrient content in PSM remained largely unaffected at 160 °C. Protein oxidation levels, infrared, and fluorescence spectra analysis revealed that higher temperatures exacerbated the oxidation of pumpkin seed emulsion. Overall, roasting raw pumpkin seeds at 160 °C is suggested to enhance PSM quality while preserving nutrient content.

Effects of high voltage pulsed electric field on structural properties and immune reactivity of arginine kinase in Fenneropenaeus chinensis

To evaluate the effect of high voltage pulsed electric field (PEF) treatment (10-20 kV/cm, 5-15 min) on the structural characteristics and sensitization of crude extracts of arginine kinase from Fenneropenaeus chinensis. By simulated in vitro gastric juice digestion (SGF), intestinal juice digestion (SIF) and enzyme-linked immunosorbent assay (ELISA), AK sensitization was reduced by 42.5% when treated for 10 min at an electric field intensity of 15 kV/cm. After PEF treatment, the α-helix content decreased, and the α-helix content gradually changed to β-sheet and β-turn. Compared to the untreated group, the surface hydrophobicity increased and the sulfhydryl content decreased. SEM and AFM analyses showed that the treated sample surface formed a dense porous structure and increased roughness. The protein content, dielectric properties, and amino acid content of sample also changed significantly with the changes in the treatment conditions. Non-thermal PEF has potential applications in the development of hypoallergenic foods.

Effects of Chlorogenic Acid on Lowering IgE-Binding Capacity of Soybean 7S: Comparison between Covalent and Noncovalent Interaction

Allergenicity of soybean 7S protein (7S) troubles many people around the world. However, many processing methods for lowering allergenicity is invalid. Interaction of 7S with phenolic acids, such as chlorogenic acid (CHA), to structurally modify 7S may lower the allergenicity. Hence, the effects of covalent (C-I, periodate oxidation method) and noncovalent interactions (NC-I) of 7S with CHA in different concentrations (0.3, 0.5, and 1.0 mM) on lowering 7S allergenicity were investigated in this study. The results demonstrated that C-I led to higher binding efficiency (C-0.3:28.51 ± 2.13%) than NC-I (N-0.3:22.66 ± 1.75%). The C-I decreased the α-helix content (C-1:21.06%), while the NC-I increased the random coil content (N-1:24.39%). The covalent 7S-CHA complexes of different concentrations had lower IgE binding capacity (C-0.3:37.38 ± 0.61; C-0.5:34.89 ± 0.80; C-1:35.69 ± 0.61%) compared with that of natural 7S (100%), while the noncovalent 7S-CHA complexes showed concentration-dependent inhibition of IgE binding capacity (N-0.3:57.89 ± 1.23; N-0.5:46.91 ± 1.57; N-1:40.79 ± 0.22%). Both interactions produced binding to known linear epitopes. This study provides the theoretical basis for the CHA application in soybean products to lower soybean allergenicity.

Insight into the allergenicity and structure changes of parvalbumin from Trachinotus ovatus induced by dense-phase carbon dioxide

Parvalbumin (PV) is a major allergen in fish, and traditional treatments cannot reduce its sensitization. The effects of dense-phase carbon dioxide (DPCD) treatment on the sensitization and spatial structure of PV in Trachinotus ovatus were evaluated in this study. Western blotting and indirect ELISA were used to determine the allergenicity changes and spatial conformations of PV treated by DPCD. Tris-tricine-SDS-PAGE, circular dichroism, surface hydrophobicity, endogenous fluorescence, UV spectrophotometry, free amino group, total sulfhydryl group and SEM analyses were applied to characterize PV structure. The results showed that DPCD treatment (15 MPa, 30 min, 50 °C) could reduce PV-induced allergic reactions by 39-41 %, which destroyed the normal conformational epitopes and reduced the risk of PV-induced allergy. The secondary structure changed from ordered to disordered with a decreased content of α-helical groups, while the internal hydrophobic groups were exposed. The total sulfhydryl group content decreased significantly (P < 0.05). The surface hydrophobicity and ultraviolet absorption spectrum were enhanced, and the endogenous fluorescence peak shifted to a long wavelength. Meanwhile, the content of free amino groups increased significantly (P < 0.05). This study could provide a theoretical basis and a promising technical approach for reduction of PV allergenicities.

Comparison of proanthocyanidins A2 and B2 on IgE-reactivity and epitopes in Gly m 6 using multispectral, LC/MS-MS and molecular docking

This study comparatively analyzed the changes in IgE-reactivity and epitopes in proanthocyanidins A2- (PA-Gly m 6) and B2-Gly m 6 (PB-Gly m 6) conjugates prepared by alkali treatment at 80 °C for 20 min. Similar to the western blot, ELISA also showed a higher reduced IgE-reactivity in PA-Gly m 6 (70.12 %) than PB-Gly m 6 (63.17 %). SDS-PAGE demonstrated that proanthocyanidins A2 caused more formation of >180 kDa polymers than proanthocyanidins B2. Multispectral analyses revealed that PA-Gly m 6 exhibited more structural alteration (e.g., a decrease of α-helical content and ANS fluorescence intensity) to unfold protein structure than proanthocyanidins B2, improving the accessibility to modify Gly m 6 for shielding or destroying conformational epitopes. LC/MS-MS revealed that PA-Gly m 6 conjugates had a lower abundance of allergens, peptides and linear epitopes than PB-Gly m 6 conjugates. Molecular docking showed that proanthocyanidins A2 and B2 reacted with Gln-317 and Asn-94 of epitopes, respectively. Overall, proanthocyanidins A2 is more effective than proanthocyanidins B2 to decrease the IgE-reactivity of Gly m 6 due to more shielding or destruction of conformational epitopes and lower content allergens and linear epitopes, which was attributed to more protein-crosslinks formation and structural changes in PA-Gly m 6 conjugates.

The alteration of composition, conformation, IgE-reactivity and functional attributes in proanthocyanidins-soy protein 7S conjugates formed by alkali-heating treatment: Multi-spectroscopic and proteomic analyses

This study assessed the alteration of IgE-reactivity and functional attribute in soy protein 7S-proanthocyanidins conjugates (7S-80PC) formed by alkali-heating treatment (pH 9.0, 80 °C, 20 min). SDS-PAGE demonstrated that 7S-80PC exhibited the formation of >180 kDa polymers, although the heated 7S (7S-80) had no changes. Multispectral experiments revealed more protein unfolding in 7S-80PC than in 7S-80. Heatmap analysis showed that 7S-80PC showed more alteration of protein, peptide and epitope profiles than 7S-80. LC/MS-MS demonstrated that the content of total dominant linear epitopes was increased by 11.4 % in 7S-80, but decreased by 47.4 % in 7S-80PC. As a result, Western-blot and ELISA showed that 7S-80PC exhibited lower IgE-reactivity than 7S-80, probably because 7S-80PC exhibited more protein-unfolding to increase the accessibility of proanthocyanidins to mask and destroy the exposed conformational epitopes and dominant linear epitopes induced by heating treatment. Furthermore, the successful attachment of PC to soy 7S protein significantly increased antioxidant activity in 7S-80PC. 7S-80PC also showed higher emulsion activity than 7S-80 owing to its high protein flexibility and protein unfolding. However, 7S-80PC exhibited lower foaming properties than 7S-80. Therefore, the addition of proanthocyanidins could decrease IgE-reactivity and alter the functional attribute of the heated soy 7S protein.

Multi-spectral and proteomic insights into the impact of proanthocyanidins on IgE binding capacity and functionality in soy 11S protein during alkali-heating treatment

This study evaluated the impact of proanthocyanidins on immunoglobulin E (IgE) binding capacity, antioxidant, foaming and emulsifying properties in soy 11S protein following alkali treatment at 80 °C for 20 min. The formation of >180 kDa polymer was observed in the combined heating and proanthocyanidins-conjugation treatment sample (11S-80PC) rather than in the heating treated sample (11S-80) using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The structural analyzes demonstrated that 11S-80PC exhibited more protein unfolding than 11S-80. Heatmap analysis revealed that 11S-80PC had more alteration of peptide and epitope profiles in 11S than in 11S-80. Molecular docking showed that PC could well react with soy protein 11S. Liquid chromatography tandem MS analysis (LC/MS-MS) demonstrated that there was a 35.6 % increase in 11S-80, but a 14.5 % decrease in 11S-80PC for the abundance of total linear epitopes. As a result, 11S-80PC exhibited more reduction in IgE binding capacities than 11S-80 owing to more obscuring and disruption of linear and conformational epitopes induced by structural changes. Moreover, 11S-80PC exhibited higher antioxidant capacities, foaming properties and emulsifying activity than 11S-80. Therefore, the addition of proanthocyanidins could decrease allergenic activity and enhance the functional properties of the heated soy 11S protein.

Investigation of the differences in the effect of (-)-epigallocatechin gallate and proanthocyanidins on the functionality and allergenicity of soybean protein isolate

In this study, the differences in effects of (-)-epigallocatechin gallate (EGCG) and proanthocyanidins (PC) on the functionality and allergenicity of soybean protein isolate (SPI) were studied. SDS-PAGE demonstrated that SPI-PC conjugates exhibited more high-molecular-weight polymers (>180 kDa) than SPI-EGCG conjugates. Structural analysis showed that SPI-PC conjugates exhibited more disordered structures and protein-unfolding, improving the accessibility of PC to modify SPI, compared to SPI-EGCG conjugates. LC/MS-MS demonstrated that PC caused more modification of SPI and major soybean allergens than EGCG, resulting in a lower abundance of epitopes. The successful attachment of EGCG and PC to SPI significantly increased antioxidant capacity in conjugates. Furthermore, SPI-PC conjugates exhibited greater emulsifying activity and lower immunoglobulin E (IgE) binding capacity than SPI-EGCG conjugates, which was attributed to more disordered structure and protein-unfolding in SPI-PC conjugates. It is implied that proanthocyanidins may be promising compounds to interact with soybean proteins to produce functional and hypoallergenic foods.

A review on polyphenols and their potential application to reduce food allergenicity

This review summarized recent studies about the effects of polyphenols on the allergenicity of allergenic proteins, involving epigallocatechin gallate (EGCG), caffeic acid, chlorogenic acid, proanthocyanidins, quercetin, ferulic acid and rosmarinic acid, etc. Besides, the mechanism of polyphenols for reducing allergenicity was discussed and concluded. It was found that polyphenols could noncovalently (mainly hydrophobic interactions and hydrogen bonding) and covalently (mainly alkaline, free-radical grafting, and enzymatic method) react with allergens to induce the structural changes, resulting in the masking or/and destruction of epitopes and the reduction of allergenicity. Oral administration in murine models showed that the allergic reaction might be suppressed by regulating immune cell function, changing the levels of cytokines, suppressing of MAPK, NF-κb and allergens-presentation pathway and improving intestine function, etc. The outcome of reduced allergenicity and suppressed allergic reaction was affected by many factors such as polyphenol types, polyphenol concentration, allergen types, pH, oral timing and dosage. Moreover, the physicochemical and functional properties of allergenic proteins were improved after treatment with polyphenols. Therefore, polyphenols have the potential to produce hypoallergenic food. Further studies should focus on active concentrations and bioavailability of polyphenols, confirming optimal intake and hypoallergenic of polyphenols based on clinical trials.

Denatured pre-treatment assisted polyphenol oxidase-catalyzed cross-linking: effects on the cross-linking potential, structure, allergenicity and functional properties of OVA

To evaluate the impacts of denatured pre-treatments (heating and denaturants) on cross-linking and the combined effect of pre-treatment and cross-linking on the structure, allergenicity and functional properties of OVA, OVA was pre-treated in different ways and then cross-linked. Results showed that the cross-linking reaction was obviously promoted with heating at 100 °C for 5 min or 0.5% of SDS as the pretreatment. Due to the coordinated process of pre-treatments and cross-linking, the secondary structure was changed and the gastrointestinal digestion of OVA was promoted. Meanwhile, the emulsifying properties, foaming properties, and antioxidant properties of OVA were remarkably improved. Furthermore, the IgG and IgE binding capacities of OVA, as well as the OVA-induced degranulation capacity of KU812 were all significantly decreased. However, upon comparing the cross-linking assisted by two different pre-treatments, it was seen that heating at 100 °C for 5 min was better than being treated with 0.5% of SDS in reducing the potential allergenicity of OVA. Therefore, we concluded that heat denaturation (at 100 °C for 5 min) assisted enzymatic cross-linking may provide a new cross-linking method to develop hypoallergenic foods with good functional properties.

Enzymatic crosslinking and food allergenicity: A comprehensive review

Food allergy has become a major global public health concern. In the past decades, enzymatic crosslinking technique has been employed to mitigate the immunoreactivity of food allergens. It is an emerging non-thermal technique that can serve as a great alternative to conventional food processing approaches in developing hypoallergenic food products, owing to their benefits of high specificity and selectivity. Enzymatic crosslinking via tyrosinase (TYR), laccase (LAC), peroxidase (PO), and transglutaminase (TG) modifies the structural and biochemical properties of food allergens that subsequently cause denaturation and masking of the antigenic epitopes. LAC, TYR, and PO catalyze the oxidation of tyrosine side chains to initiate protein crosslinking, while TG initiates isopeptide bonding between lysine and glutamine residues. Enzymatic treatment produces a high molecular weight crosslinked polymer with reduced immunoreactivity and IgE-binding potential. Crosslinked allergens further inhibit mast cell degranulation due to the lower immunostimulatory potential that assists in the equilibration of T-helper (Th)1/Th2 immunobalance. This review provides an updated overview of the studies carried out in the last decade on the potential application of enzymatic crosslinking for mitigating food allergenicity that can be of importance in the context of developing hypoallergenic/non-allergenic food products.

Quantification of crustacean tropomyosin in foods using high-performance liquid chromatography-tandem mass spectrometry method

BACKGROUND

Allergic reactions to crustacean products have been increasing owing to the rising consumption. Tropomyosin (TM) is the main crustacean allergen; it has a coiled-coil structure, which shows stability to various food processing methods. Crustacean processed products have been used in several food products, thereby causing greater difficulties in detecting TM in these products. We aimed to develop an assay based on high-performance liquid chromatography-tandem mass spectrometry for the accurate and reproducible quantification of crustacean TM in foods.

RESULTS

The three peptides IQLLEEDLER, LAEASQAADESER, and IVELEEELR were selected as peptide markers, and the peptide IVELEEELR was selected as the quantitative marker. Extraction conditions and enzymatic digestion conditions were completely optimized. The extraction solution of Tris-hydrochloric acid buffer (50 mmol L^-1 , pH 7.4) containing 1 mol L^-1 potassium chloride and the enzymatic treatment at 1:15 ratio (enzyme/protein, m/m) for 13 h showed excellent efficiency. The method exhibited a good linear relationship, with the qualified coefficient of determination (R²  = 0.9994) in the wide range of 1 to 1000 μg L^-1 . The accuracy was validated based on spiked recovery at three spiking levels (12.5, 25.0, and 50.0 μg kg^-1 , TM/matrix) in blank matrices that included chicken sausages, beef balls, and egg-milk biscuits. The recoveries ranged from 91% to 109% with qualified relative standard deviations <15% with the limit of quantification (of 1.6 mg kg^-1 , TM/matrix).

CONCLUSION

This new approach can be used for the qualitative and quantitative detection of crustacean TM in various food matrices. © 2021 Society of Chemical Industry.

Whey allergens: Influence of nonthermal processing treatments and their detection methods

Whey and its components are recognized as value-added ingredients in infant formulas, beverages, sports nutritious foods, and other food products. Whey offers opportunities for the food industrial sector to develop functional foods with potential health benefits due to its unique physiological and functional attributes. Despite all the above importance, the consumption of whey protein (WP) can trigger hypersensitive reactions and is a constant threat for sensitive individuals. Although avoiding such food products is the most successful approach, there is still a chance of incorrect labeling and cross-contamination during food processing. As whey allergens in food products are cross-reactive, the phenomenon of homologous milk proteins of various species may escalate to a more serious problem. In this review, nonthermal processing technologies used to prevent and eliminate WP allergies are presented and discussed in detail. These processing technologies can either enhance or mitigate the impact of potential allergenicity. Therefore, the development of highly precise analytical technologies to detect and quantify the existence of whey allergens is of considerable importance. The present review is an attempt to cover all the updated approaches used for the detection of whey allergens in processed food products. Immunological and DNA-based assays are generally used for detecting allergenic proteins in processed food products. In addition, mass spectrometry is also employed as a preliminary technique for detection. We also highlighted the latest improvements in allergen detection toward biosensing strategies particularly immunosensors and aptasensors.

The conformational structural change of β-lactoglobulin via acrolein treatment reduced the allergenicity

•

Acrolein induced structural changes through the cross-linking of BLG.

•

The IgE binding capacity of BLG was reduced upon acrolein treatment.

•

Stimulation with acrolein-treated BLG decreased RBL-2H3 cells degranulation rates.

•

BLG-specific IgE/IgG1, histamine and mMCP-1 levels were reduced in mice model.

•

Structural changes resulted in reduction of BLG allergenicity by lipid peroxidation.

β-lactoglobulin (BLG) is a major allergen of milk. Since lipid peroxidation such as acrolein commonly exists during milk processing, it is necessary to evaluate its influence on BLG structure and potential allergenicity. The structure of acrolein-treated BLG was detected using SDS-PAGE, fluorescence, ultraviolet spectrum (UV), circular dichroism (CD) and LC-MS-MS, and the potential allergenicity was assessed by in vitro and in vivo assays. Results showed that acrolein could cause structural changes by BLG aggregation, which decreased the IgE binding capacity. Further, the release of mediators and cytokines decreased with acrolein treatment in RBL-2H3 cells. Mice showed lower allergenicity by the levels of BLG-specific antibody and the release of histamine and mMCP-1. These results explained that acrolein-induced BLG aggregation could damage the allergic epitopes and decrease the allergenicity of BLG in milk. The study will provide a new aspect to explore the natural phenomenon of allergen changes during food processing.

Effect of sarcoplasmic proteins oxidation on the gel properties of myofibrillar proteins from pork muscles

This study investigated the influence of sarcoplasmic proteins (SPs) treated by the oxidation system (0.1 mmol/L FeCl₃ , 0.1 mmol/L ascorbic acid, and 0, 1, 5, 10 mmol/L H₂ O₂ ) on the properties of pork myofibrillar proteins (MPs) gel. After oxidation treatment, the SPs showed an increased in carbonyl content and a decreased in total sulfhydryl content, coupled with the cross-linking of protein components by disulfide bonds and covalent bonds. The MPs gel with SPs oxidized at 1 mmol/L H₂ O₂ exhibited the maximal strength while the minimal water holding capacity (WHC). The WHC of MPs gel was significantly decreased with increasing SPs oxidation, leading to the increase of free water and the decrease of immobilized water in the gel system. The microstructures of MPs gels with moderately (1 mmol/L H₂ O₂ ) oxidized SPs showed a more compact and smaller pore gel network than MPs alone, suggesting adding oxidized SPs can expel water trapped in the gel. Furthermore, the environmental polarity of aliphatic C-H groups increased with SPs oxidation.

Immunostimulatory and allergenic properties of emulsified and non-emulsified digestion products of parvalbumin (Scophthalmus maximus) in RBL-2H3 cells and BALB/c mouse models

In the present study, the influence of lipid emulsion on the allergenicity of digestion products of fish parvalbumin (PV) was investigated, which was initially subjected to simulated gastric/intestinal digestion both under emulsified and non-emulsified conditions. The release of β-hexosaminidase (β-hex), histamine (His), tryptase (TPS), interleukin 4 (IL-4), and IL-13 in RBL cells was decreased by 79.32, 26.19, 41.67, 53.95 and 54.40%, respectively, following stimulation with the gastric digestion products of PV. Whereas, lipid emulsified digestion products of PV (e-PV) significantly enhanced the release of active mediators and cytokines. The digestion products of emulsified PV at 180 min resulted in a higher release of β-hex (197.60%), His (12.18%), TPS (38.85%), IL-4 (48.19%) and IL-13 (59.40%), as compared to that of PV. However, no obvious differences in the release of active substances and cytokines were noted between intestinal digestion products of PV and intestinal digestion products of emulsified PV. In the mouse model studies, digested PV products reduced the anaphylactic scores, whereas e-PV manifested a higher level of allergic symptoms. Moreover, mice treated with 50% e-PV had significantly higher levels of specific IgE (32.56%), total IgE (16.67%) and total IgG1 (5.15%) than those treated with 50% PV. Mice treated with 50% e-PV had significantly higher levels of His (8.50%) and TPS (10.07%) compared with mice treated with 50% PV. Lipid emulsions altered the digestibility of PV in gastrointestinal digestion and enhanced the allergenicity of PV digestion products at the cellular levels, subsequently posing a higher risk of allergic reactions in susceptible individuals.

Comparison of digestibility and potential allergenicity of raw shrimp (Litopenaeus vannamei) extracts in static and dynamic digestion systems

In this work, a simplified dynamic digestion system was developed, and used for comparing the digestibility and potential allergenicity of raw shrimp extracts (RSE) in static and dynamic digestion systems. Protein hydrolysis was analyzed by electrophoresis, and the potential allergenicity was reflected in IgG/IgE binding ability and activation of basophils. In comparison with static digestion, protein hydrolysis indicated different kinetic behaviors, especially tropomyosin (TM) showed better digestion stability during dynamic digestion. The potential allergenicity of RSE exhibited different changing trends with digestion in the two systems. However, the apparent molecular weight (Mw) of immune fragments (>11 kDa) showed good approximation, and the IgE-binding fragment near 70 kDa revealed outstanding digestion stability than primordial protein in both systems. In conclusion, the dynamic conditions had a significant impact on the assessment of the persistence and potential allergenicity of digestion-resistant allergens, while the apparent Mw of IgG/IgE binding hydrolysate was not affected.

Crosslinked Recombinant-Ara h 1 Catalyzed by Microbial Transglutaminase: Preparation, Structural Characterization and Allergic Assessment

As the one of the major allergens in peanut, the allergenicity of Ara h 1 is influenced by its intrinsic structure, which can be modified by different processing. However, molecular information in this modification has not been clarified to date. Here, we detected the influence of microbial transglutaminase (MTG) catalyzed cross-linking on the recombinant peanut protein Ara h 1 (rAra h 1). Electrophoresis and spectroscopic methods were used to analysis the structural changes. The immunoreactivity alterations were characterized by enzyme linked immunosorbent assay (ELISA), immunoblotting and degranulation test. Structural features of cross-linked rAra h 1 varied at different reaction stages. Hydrogen bonds and disulfide bonds were the main molecular forces in polymers induced by heating and reducing. In MTG-catalyzed cross-linking, ε-(γ-glutamyl) lysine isopeptide bonds were formed, thus inducing a relatively stable structure in polymers. MTG catalyzed cross-linking could modestly but significantly reduce the immunoreactivity of rAra h 1. Decreased content of conserved secondary structures led to a loss of protection of linear epitopes. Besides, the reduced surface hydrophobic index and increased steric hindrance of rAra h 1 made it more difficult to bind with antibodies, thus hindering the subsequent allergic reaction.

Natural Shrimp (Litopenaeus vannamei) Tropomyosin Shows Higher Allergic Properties than Recombinant Ones as Compared through SWATH-MS-Based Proteomics and Immunological Response

Tropomyosin (TM) is the major shrimp allergen that could trigger anaphylactic reactions. Recently, recombinant TM (rTM) has been accepted widely in the field of allergen-specific immunotherapy, but the allergenicity of rTM has not been compared with natural TM (nTM) based on an in vitro digestion profile. In this work, IgG-/IgE binding, allergen peptides, and degranulation ability of the digested samples in simulated gastric fluid/simulated intestinal fluid/gastrointestinal models from nTM and rTM were evaluated by immunoassays, proteomics, and basophil degranulation assay. Results showed that pepsin-digested and trypsin-digested samples of rTM exhibited lower IgG-/IgE binding and degranulation than those of nTM. More peptides of the digested samples from rTM (57.8%) matched shrimp allergic epitopes than those from nTM (33.3%). However, the peptide SITDELDQTF (269-278) appeared most frequently. These findings would supply foundation data for epitope-based immunotherapy to shrimp allergic individuals.

Tyrosinase/caffeic acid cross-linking alleviated shrimp (Metapenaeus ensis) tropomyosin-induced allergic responses by modulating the Th1/Th2 immunobalance

In this study, the effect of enzymatic cross-linking of shrimp tropomyosin (TM) with tyrosinase and caffeic acid (TM-Tyr/CA) on the allergic response were assessed using in vitro and in vivo models. The RBL-2H3 and KU812 cell lines were employed to evaluate the changes in the stimulation abilities of TM-Tyr/CA that showed significant inhibition of mediators and cytokines. The digestibility of cross-linked TM was improved and the recognitions of IgG/IgE were markedly reduced, as revealed by western blotting. TM-Tyr/CA decreased anaphylactic symptoms, and hindered the levels of IgG1, IgE, histamine, tryptase and mouse mast-cell protease-1 (mMCP-1) in mice sera. Cross-linked TM downregulated the production of interleukin (IL)-4, IL-5, and IL-13 by 51.36, 12.24 and 20.55%, respectively, whereas, IL-10 and IFN-γ were upregulated by 20.71 and 19.0%. TM-Tyr/CA showed reduced allergenicity and may have preventive effect in relieving TM induced allergic response via immunosuppression and positive modulation of T-helper (Th)1/Th2 immunobalance.

Immunomodulatory Effect of Laccase/Caffeic Acid and Transglutaminase in Alleviating Shrimp Tropomyosin (Met e 1) Allergenicity

This work aimed to investigate the effect of enzymatic cross-linking on the allergenic potential of shrimp tropomyosin (TM), Met e 1. The cross-linked TM with laccase (CL), laccase/caffeic acid (CLC and CLC⁺), and transglutaminase (CTG and CTG⁺) formed macromolecules and altered the allergen conformation. The IgG/IgE-binding potentials of the cross-linked TM were reduced as confirmed by Western blotting and ELISA. Enzymatic cross-linking improved the gastrointestinal digestibility and induced a lower level of degranulation in RBL-2H3 and KU812 cells. Moreover, cross-linked TM decreased anaphylactic symptoms, as well as reduced the serum levels of IgG1, IgE, histamine, tryptase, and mMCP-1. In spleen cells, CLC⁺ and CTG⁺ downregulated the Th2-related cytokines and upregulated IFN-γ and IL-10. These findings revealed that CTG⁺ has shown more potential than CLC⁺ in mitigating the allergenicity of TM by influencing the conformational structure, enhancing the digestibility, decreasing the cellular degranulation process, and positively modulating the Th1/Th2 immunobalance.

Identification and Characterization of the Tyrosinase Inhibitory Activity of Caffeine from Camellia Pollen

Tyrosinase inhibitors are important in cosmetic, medical, and food industries due to their regulation of melanin production. A tyrosinase inhibitor was purified from Camellia pollen using high-speed countercurrent chromatography and preparative high-performance liquid chromatography and was identified as caffeine by NMR and mass spectrometry. It showed strong mushroom tyrosinase inhibitory activity with an IC₅₀ of 18.5 ± 2.31 μg/mL in a noncompetitive model. The caffeine did not interact with copper ions in the active center of the enzyme but could quench fluorescence intensity and change the secondary conformation of this tyrosinase. A molecular dynamics simulation showed that caffeine bound this tyrosinase via Lys379, Lys 376, Asp357, Glu356, Thr308, Gln307, Asp312, and Trp358, thus changing the binding sites of l-tyrosine and the loop conformation adjacent to the active center. In vitro cell model analysis revealed that caffeine exhibited significant inhibitory effects on both intracellular tyrosinase activity and melanin production of B16-F10 melanoma cells in a concentration-dependent manner. These comprehensive results suggest that caffeine is a strong tyrosinase inhibitor that has the potential to be developed as skin-whitening agents in the cosmetics and pharmaceutical industries or as antibrowning agents in the food industry.

Effect of tyrosinase and caffeic acid crosslinking of turbot parvalbumin on the digestibility, and release of mediators and cytokines from activated RBL-2H3 cells

Turbot can induce allergy in susceptible individuals due to the presence of parvalbumin (PV), a major fish allergen. This study aimed at evaluating the digestibility and the ability of PV to elicit the release of cellular degranulation, following treatment with tyrosinase (PV-Tyr), caffeic acid (PV-CA) and in combination (PV-Tyr/CA), using in vitro digestion and RBL-2H3 (passive rat basophil leukemia) cell line. The digestion assay products revealed that the stability of PV in simulated gastric fluid (SGF) was stronger, while in simulated intestinal fluid (SIF) was rather weak. Western blot analysis revealed that the IgG-binding abilities of the cross-linked PV were markedly reduced. Moreover, crosslinking hampered the release of cellular degranulation process in RBL-2H3 cell lines. PV-Tyr/CA showed highly significant reduction in the release rate of β-hexosaminidase (66.02%), histamine (35.01%), tryptase (29.25%), cysteinyl leukotrienes (29.72%), prostaglandin D₂ (34.96%), IL-4 (43.99%) and IL-13 (38.93%) and shown potential in developing hypoallergenic fish products.

Effect of tyrosinase-catalyzed crosslinking on the structure and allergenicity of turbot parvalbumin mediated by caffeic acid

BACKGROUND

Enzymatic treatment of allergenic protein can alter their functional properties under a mild reaction condition due to specificity of enzymes. Phenolic compounds act as mediators and enhance the crosslinking reactions. The study aimed to assess the changes in the structure and immunoglobulin G (IgG) binding capacity of turbot parvalbumin (PV) upon crosslinking with tyrosinase (Tyr) in the absence and presence of caffeic acid.

RESULTS

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed the appearance of higher molecular weight bands (24, 36 kDa) in the crosslinked PV. The secondary structure of crosslinked PV became loosened and disordered. The results of intrinsic fluorescence and ultraviolet absorption spectral analyses, as well as surface hydrophobicity and free amino group analyses also revealed structural changes. As observed by western blot analysis, the intensity of the PV bands reduced upon Tyr treatment, indicating reduced binding of specific IgG to PV. Moreover, the indirect ELISA (enzyme-linked immunosorbent assay) analysis confirmed that the IgG binding ability of crosslinked PV was reduced 34.94%.

CONCLUSION

Enzymatic treatment mitigated the allergenicity of fish PV, which was closely related to the alterations in the conformational structure. This treatment showed potential for developing hypoallergenic fish products under mild reaction conditions. © 2019 Society of Chemical Industry.

Identification and comparison of allergenicity of native and recombinant fish major allergen parvalbumins from Japanese flounder (Paralichthys olivaceus)

Compared with native parvalbumin, recombinant β-parvalbumin based on the optimized DNA sequence can be used in fish allergen confirmation.

Cross-linking of shrimp tropomyosin catalyzed by transglutaminase and tyrosinase produces hypoallergens for potential immunotherapy

Transglutaminase or tyrosinase treatment reduces tropomyosin allergenicity and produces potential hypoallergens for immunotherapy.

Impacts of glycation and transglutaminase-catalyzed glycosylation with glucosamine on the conformational structure and allergenicity of bovine β-lactoglobulin

β-Lactoglobulin (β-LG) is recognized as the major milk allergen. In this study, the effects of transglutaminase (TGase) and glucosamine (GlcN)-catalyzed glycosylation and glycation on the conformational structure and allergenicity of β-LG were investigated. The formations of cross-linked peptides were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and GlcN-conjugated modification was identified using matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Structural analysis revealed that glycosylation and glycation of β-LG induced unfolding of the primary protein structure followed by a loss of the secondary structure. As revealed by circular dichroism (CD) spectroscopy, glycosylated β-LG exhibited the highest increase in the β-sheets from 32.6% to 40.4% (25 °C) and 44.2% (37 °C), and the percentage of α-helices decreased from 17.7% to 14.4% (25 °C) and 12.3% (37 °C), respectively. The tertiary and quaternary structures of β-LG also changed significantly during glycosylation and glycation, along with reduced free amino groups and variation in surface hydrophobicity. Immunoblotting and indirect enzyme-linked immuno sorbent assay (ELISA) analyses demonstrated that the lowest IgG- and IgE-binding capacities of β-LG were obtained following glycosylation at 37 °C, which were 52.7% and 56.3% lower than that of the native protein, respectively. The reduction in the antigenicity and potential allergenicity of glycosylated β-LG was more pronounced compared to TGase treated- and glycated β-LG, which correlated well with the structural changes. These results suggest that TGase-catalyzed glycosylation has more potential compared to glycation for mitigating the allergenic potential of milk products.