title: Determination of pepsin-susceptible and pepsin-resistant epitopes in native and heat-treated peanut allergen Ara h 1.
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.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Evelien L
authors.initials: EL
authors.lastname: van Boxtel
authors.forename: Stef J
authors.initials: SJ
authors.lastname: Koppelman
authors.forename: Lambertus A M
authors.initials: LA
authors.lastname: van den Broek
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
mesh_terms: D000485:Allergens / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D002918:Chymotrypsin / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006023:Glycoproteins / Q000276:immunology / Q000378:metabolism*; D006358:Hot Temperature; D006868:Hydrolysis; D007073:Immunoglobulin E / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010434:Pepsin A / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000485:Allergens; D052179:Antigens, Plant; C500889:Ara h 1 protein, Arachis hypogaea; D000939:Epitopes; D006023:Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D010940:Plant Proteins; D007073:Immunoglobulin E; D002918:Chymotrypsin; D010434:Pepsin A