Contribution of Chemical Modifications and Conformational Epitopes to IgE Binding by Ara h 3

Abstract

Roasting is known to change the allergenic properties of peanuts. To study these observations at a molecular level, the relationship of IgE binding to the structure of Ara h 3 from raw and roasted peanuts was assessed. Ara h 3 (A3) was purified from raw (R), light roast (LR) and dark roast (DR) peanuts, the purity was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the secondary structures were compared with circular dichroism (CD) spectroscopy. In order to understand the contribution of structure to IgE binding, the R A3 was partially denatured (PD) by heat treatment (65 °C for 2 h), subjected to CD spectroscopy and IgE spot blot analysis with sera from peanut- allergic individuals. While we observed that the secondary structure of purified A3 from R and LR peanut in solution was affected by the reduction of disulfide bonds and heat treatment when purified from the peanut following the roasting process, only small alterations were seen in the secondary structure. The purified LR A3 bound higher levels of IgE than the RA3. CD spectroscopy of PD A3 revealed a reduction in the percentage of alpha helices, and serum IgE binding. Therefore, while A3 purified from roasted peanuts did not show significant changes in secondary structure, it showed higher IgE binding than R A3. Therefore, the higher IgE binding to LR A3 was more likely to be due to chemical modifications than structural changes. However, a decrease in the IgE binding was seen if R A3 was deliberately unfolded, indicating that the structure played an important role in IgE binding to A3.

Thermal Processing of Peanut Grains Impairs Their Mimicked Gastrointestinal Digestion While Downstream Defatting Treatments Affect Digestomic Profiles

“…Moreover, it is obvious that the thermal processing dramatically affected the pepsin resistance of the acidic subunit of Ara h 3, since the 35 kDa bands are visible in the digests of the raw peanuts, but not in the digests of boiled peanuts (Figure 4). The roasting of peanuts affected Ara h 3 in a similar manner as Ara h 1; aggregates were formed and the ability to bind the IgE antibodies was increased [24].…”

Peanut Allergy: Characteristics and Approaches for Mitigation

“…Processing methods such as heat (roasting, boiling, and frying), chemical treatment, acidic and enzymatic hydrolysis, and other novel technologies such as ultrasonication, high pressure processing (HPP), irradiation, pulsed ultraviolet light (PUV), pulsed electric field (PEF), and combined processing (Hurdle technology) have been explored to reduce IgE reactivity and allergenicity of peanut. Processing technology has the capability of altering the protein structure, function, and physicochemical properties of peanuts (Dyer et al., ; Maleki, ; Maleki et al., ; Maleki & Hulburt, ; Nesbit et al., ; Nesbit, Chung, Hulburt, & Maleiki ). The alteration of allergenic proteins influences its immunoreactivity either positively or negatively by structural unfolding, aggregation, degradation, and crosslinking, which can influence the allergenicity.…”

“…The alteration of allergenic proteins influences its immunoreactivity either positively or negatively by structural unfolding, aggregation, degradation, and crosslinking, which can influence the allergenicity. A key mechanism in reducing protein allergenicity is to alter its structural and linear immunoglobulin E (IgE) binding sites (epitopes) (Comstock, Maleki, & Teuber, ; Dyer et al., ; Huang, Yang, & Wang, ; Khan et al., ; Li, Yu, Ahmedna, & Goktepe, ; Maleki et al., ; Nesbit et al., ; O'Konek et al., ; Rahaman, Vasiljevic, & Ramchandran, ; Vanga, Singh, & Raghavan, ). Enzymatic hydrolysis and hurdle techniques have the greatest potential to alter allergenic proteins while covalent modifications such as crosslinking, aggregation, oxidation, reduction, alkylation, and acylation also impart significant alteration in allergenicity (Cabanillas et al., ; Chung & Champagne, ; Kasera, Singh, Lavasa, Prasad, & Arora, ; Mikiashvili & Yu, ; Yu, Ahmedna, Goktepe, Cheng, & Maleki, ).…”

“…Destruction of conformational epitopes may expose masked epitopes while linear epitopes may be altered by chemical and enzymatic hydrolysis (Kasera et al, 2015;Lee et al, 2016;Rahaman et al, 2016). Besides IgE epitopes, protein structure also plays a critical role and functions in the allergenic potential of proteins (Chruszcz et al, 2011, Nesbit et al, 2012, Dyer et al, 2018Maleki, Kopper et al, 2000;Maleki et al, 2003, Maleki, 2004, Maleki & Hurlburt, 2004. Therefore, the alteration in allergen structure subsequently alters its physicochemical properties such as solubility and digestibility, which in turn plays a significant role in altering the immunoreactivity (Apostolovic et al, 2013;Mikiashvili & Yu, 2018;Plundrich et al, 2015;Szymkiewicz & Jędrychowski, 2009;Vanga et al, 2016).…”

Functional Uses of Peanut (Arachis hypogaea L.) Seed Storage Proteins

“…Among different proteins, glycinin is nutritionally superior to the 7S con-glycinins [69], and possesses superior intrinsic functional properties for processed foods [70]. Processing technology has the capability of altering the protein structure, function, and physicochemical properties of peanuts [71][72][73][74][75][76].…”