Digestion of peanut allergens Ara h 1, Ara h 2, Ara h 3, and Ara h 6: a comparative in vitro study and partial characterization of digestion-resistant peptides.
METHODS
There are differences in stability to pepsin between the major allergens in peanut; however, data are from different reports using different digestion models. This study provides a comprehensive comparison of the digestibility of the major peanut allergens.


RESULTS
Peanut allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 were incubated with pepsin to mimic the effect of gastric digestion. Samples were analyzed using SDS-PAGE. To further investigate resistance to digestion, Ara h 2 was additionally subjected to digestion with trypsin and residual peptides were characterized. Ara h 1 and Ara h 3 were rapidly hydrolyzed by pepsin. On the contrary, Ara h 2 and Ara h 6 were resistant to pepsin digestion, even at very high concentrations of pepsin. In fact, limited proteolysis could only be demonstrated by SDS-PAGE performed under reducing conditions, indicating an important role for the disulfide bridges in maintaining the quaternary structure of Ara h 2 and Ara h 6. Trypsin digestion of Ara h 2 similarly resulted in large residual peptides and these were identified.


CONCLUSIONS
Ara h 2 and Ara h 6 are considerably more stable towards digestion than Ara h 1 and Ara h 3.
Koppelman
Stef J
SJ
TNO Quality of Life, Zeist, The Netherlands. skoppelman@hal-allergy.nl
Hefle
Sue L
SL
Taylor
Steve L
SL
de Jong
Govardus A H
GA
D055516:2S Albumins, Plant / Q000378:metabolism*; D000485:Allergens / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000378:metabolism*; D010367:Arachis; D004063:Digestion; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010434:Pepsin A / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D055314:Seed Storage Proteins / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
D055516:2S Albumins, Plant; D000485:Allergens; D052179:Antigens, Plant; C500889:Ara h 1 protein, Arachis hypogaea; C500890:Ara h 2 allergen, Arachis hypogaea; C492737:Ara h 6 allergen, Arachis hypogaea; D006023:Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D010940:Plant Proteins; D055314:Seed Storage Proteins; C118207:allergen Ara h3; D014357:Trypsin; D010434:Pepsin A