Proteomika posttranslacionih i hemijskih modifikacija proteina i interakcije proteina od značaja u alergiji na hranu

Abstract

Alergija na hranu je reakcija preosetljivosti imunskog sistema na hranu koja dovodi do stvaranja IgE antitela. Ne postoji efikasan tretman i izbegavanje namirnica koje izazivaju simptome je jedini način za sprečavanje ozbiljnih posledica. Cilj ove teze je izučavanje posttranslacionih i hemijskih modifikacija (PTM i HM) i interakcija alergena hrane sa biološki aktivnim polifenolom biljnog porekla. Alergija na crveno meso je novootkriveni tip odložene reakcije, sa PTM galaktozil-α-1,3- galaktozom (α-Gal) kao epitopom. Ispitani su podložnost model proteina - tiroglobulina (TG) digestiji pepsinom, prisustvo α-Gal na rezultujućim peptidima i pretpostavljeno mesto vezivanja α-Gal za TG. Pokazano je da je α-Gal celim tokom simulirane želudačne digestije vezan za nastale peptide TG, koji zadržavaju sposobnost da vežu IgE. Alergija na kikiriki je među najopasnijim zbog učestalosti, postojanosti i ozbiljnosti simptoma. Postoje razlike u alergenosti između sirovog i pečenog kikirikija, koje mogu poticati od razlika u modifikacijama alergena. U ovoj disertaciji je proučena razlika u modifikacijama glavnih alergena iz sirovog i pečenog kikirikija. Detektovano je 27 modifikacija, od kojih 4 isključivo na proteinima pečenog kikirikija. Pokazane su razlike u profilima modifikacija proteina između ekstrakata, koje mogu uticati na alergenost. 2S albumini kikirikija su zbog kompaktne strukture otporni na delovanje digestivnih enzima, što se povezuje sa njihovom alergenošću. Ispitane su interakcije između njih i epigalokatehin-3-galata (EGCG), katehina zelenog čaja sa imunomodulatornim svojstvima koji pospešuje digestiju proteina pepsinom. Vezivanje EGCG-a za alergene izaziva promene u njihovoj strukturi (entalpijski povoljan proces), sa konstantama vezivanja reda veličine 104 M-1.

Food allergy is an immune system reaction to certain foods that results in IgE antibody generation. Efficient treatment does not exist, so avoidance of trigger foods is the only way to prevent serious consequences. The aim of this thesis was to study posttranslational and chemical modifications (PTM and CM) of food allergens and their interactions with biologically active plant polyphenol. Red meat allergy is a newly discovered type of allergy with delayed symptoms and a PTM - galactose-α-1,3-galactose (α-Gal) as an epitope. Digestibility of a model protein - thyroglobulin (TG) by pepsin and presence of α-Gal on resulting peptides was studied, and the position of α-Gal containing glycan on TG was proposed. It was shown that throughout simulated gastric digestion α-Gal remains bound to IgE reactive TG peptides. Peanut allergy is among most dangerous types of food allergies due to prevalence, persistence and symptom severity. Differences in allergenicity between raw and roasted peanuts were previously shown and might stem from differences in protein modifications. Differences in major allergen modifications between raw and roasted peanut were studied. Twenty-seven modifications were detected, 4 of which exclusively on allergens from roasted peanuts. Differences in modification profiling were found between the two protein preparations that can affect their allergenicity. Peanut 2S albumins are compact digestion-resistant proteins, which attributes to their allergenicity. Their interactions with epigallocatechin-3-gallate (EGCG), an immunomodulatory green tea catechin that facilitates pepsin digestion of proteins were studied. The results show that binding of EGCG to these allergens induces conformational changes, and is enthalpy favorable with binding constants of 104 M-1.