|Dinter, Jens - Harvard Institute Of Medicine|
|Berberich, Matthew - Harvard University|
|Chung, Si Yin|
|Le Gall, Sylvie - Harvard University|
Submitted to: Food Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2015
Publication Date: 2/10/2015
Citation: Mattison, C.P., Dinter, J., Berberich, M.J., Chung, S., Reed, S.S., Le Gall, S., Grimm, C.C. 2015. In vitro evaluation of digestive and endolysosomal enzymes to cleave CML-modified Ara h 1 peptides. Food Science and Nutrition. doi: 10.1002/fsn3.215.
Interpretive Summary: Food allergy reactions are Type I hypersensitivities provoked by immunoglobulin E (IgE)-binding to specific proteins within foods. The sensory and biological characteristics of food proteins can be modified during cooking or processing. These modifications may modulate the ability of food allergens, such as the Ara h 1 peanut allergen, to cause allergy. Carboxymethyl-lysine (CML) modification is a previously described non-enzymatic modification on food proteins. Using model systems we tested the ability of digestive and cellular proteases to cleave CML modified and unmodified synthetic Ara h 1 peptides. Analyses of the digested peptides, using sensitive chemical and molecular methods, indicates that CML modification can make proteins resistant to digestion with the intestinal protease trypsin. Our findings suggest that processing induced protein modifications could directly contribute to making food allergens more potent by acting to protect proteins and IgE epitopes from digestion by proteases.
Technical Abstract: The sensory, biological, chemical, and immunological characteristics of foods can be modified non-enzymatically during processing. Notably, these modifications may modulate the allergenic potency of food allergens, such as the Ara h 1 peanut allergen. Carboxymethyl-lysine (CML) modification is a previously described non-enzymatic modification on food proteins. In the current study, we tested the ability of digestive and endolysosomal proteases to cleave CML modified and unmodified synthetic Ara h 1 peptides. Proteomic analyses of the digested peptides, using electrospray liquid chromatography/mass spectrometry (LC/MS), demonstrates that carboxymethylation of lysine residues renders these peptides refractory to trypsin digestion in simulated intestinal fluid. We did not detect observable differences in the simulated gastric fluid or endolysosomal digestion between the parental and CML modified peptides. One of the tested peptides contains a lysine residue previously shown to be CML modified, and it lies in a previously mapped linear IgE epitope, but we did not observe a difference in IgE binding between the modified and parental peptides. Our findings suggest a molecular mechanism for the increased resistance of peanut allergens modified by thermal processing, such as Ara h 1, to digestion in intestinal fluid after heating and could help explain how food processing-induced modifications may lead to more potent food allergens by acting to protect intact IgE epitopes from digestion by proteases targeting lysine residues.