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Determination of pepsin-susceptible and pepsin-resistant epitopes in native and heat-treated peanut allergen Ara h 1

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Author: Boxtel, E.L. van · Koppelman, S.J. · Broek, L.A.M. van den · Gruppen, H.
Type:article
Date:2008
Institution: TNO Kwaliteit van Leven · KvL
Source:Journal of Agricultural and Food Chemistry, 6, 56, 2223-2230
Identifier: 240710
doi: doi:10.1021/jf072907n
Keywords: Agriculture · Ara h 1 · Epitopes · Food allergy · IgE binding · Mass spectrometry · allergen · Ara h 1 protein, Arachis hypogaea · chymotrypsin · epitope · glycoprotein · immunoglobulin E · pepsin A · peptide fragment · vegetable protein · amino acid sequence · article · chemistry · heat · hydrolysis · immunology · metabolism · molecular genetics · molecular weight · Allergens · Amino Acid Sequence · Chymotrypsin · Epitopes · Glycoproteins · Heat · Hydrolysis · Immunoglobulin E · Molecular Sequence Data · Molecular Weight · Pepsin A · Peptide Fragments · Plant Proteins · Ara · Arachis hypogaea

Abstract

This study was aimed at the determination of the pepsin-susceptible and pepsin-resistant epitopes in native and heat-treated Ara h 1, a major allergen from peanuts. Both the oligomeric structure and the trimeric structure of the allergen were investigated. Under the in vitro conditions applied, oligomeric Ara h 1, either unheated or preheated, was hydrolyzed by pepsin at a lower rate than trimeric Ara h 1. Peptides with relatively high molecular masses were shown to be able to bind IgE, whereas peptides with lower molecular masses (<2 kDa) did not. In these latter fractions, fragments of 15 previously published epitopes of mature Ara h 1 were identified. As a result, these epitopes are not likely responsible for the induction of systemic food allergic reactions to peanuts. Using sequential chymotrypsin digestion, the pepsin-resistant IgE-binding peptides were deduced to contain the previously identified intact epitopes EDWRRPSHQQ (amino acids 50-59) and PRKIRPEG (amino acids 60-67). The presence of four additional earlier published intact epitopes (covering amino acids 6-13, 14-21, 24-31, and 40-47) on the pepsin-resistant peptides could be neither deduced nor ruled out. The two deduced and four possible pepsin-resistant epitopes are all situated in the N-terminal part of Ara h 1, which does not show homology with other vicilin proteins. Consequently, this unique N-terminal part of Ara h 1 is proposed to be responsible for the allergen's ability to induce systemic allergic reactions. © 2008 American Chemical Society. Chemicals / CAS: chymotrypsin, 9004-07-3, 9014-64-6; immunoglobulin E, 37341-29-0; pepsin A, 9001-75-6; Allergens; Ara h 1 protein, Arachis hypogaea; Chymotrypsin, EC 3.4.21.1; Epitopes; Glycoproteins; Immunoglobulin E, 37341-29-0; Pepsin A, EC 3.4.23.1; Peptide Fragments; Plant Proteins