Identification and Characterization of Ana o 3 Modifications on Arginine-111 Residue in Heated Cashew Nuts

• Published in: Journal of agricultural and food chemistry 2017-01, Vol.65 (2), p.411-420
• Main Authors: Mattison, Christopher P, Grimm, Casey C, Li, Yichen, Chial, Heidi J, McCaslin, Darrell R, Chung, Si-Yin, Bren-Mattison, Yvette, Wasserman, Richard L
• Format: Article
• Language: English
• Subjects: Anacardium - chemistry; Antigens, Plant - chemistry; Antigens, Plant - isolation & purification; Antigens, Plant - metabolism; Arginine - chemistry; Circular Dichroism; Dynamic Light Scattering; Enzyme-Linked Immunosorbent Assay; Food Handling - methods; Heating; Humans; Imidazoles - chemistry; Immune Sera; Immunoglobulin E - metabolism; Nut Hypersensitivity - immunology; Nuts - chemistry; Particle Size; Plant Proteins - chemistry; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Protein Conformation; Trypsin - chemistry
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.6b04134

Raw and roasted cashew nut extracts were evaluated for protein modifications by mass spectrometry. Independent modifications on the Arg-111 residue of Ana o 3 were observed in roasted but not raw cashew nuts. The mass changes of 72.0064 or 53.9529 Da are consistent with the formation of carboxyethyl and hydroimidazolone modifications at the Arg-111 residue. These same modifications were observed in Ana o 3 purified from roasted but not raw cashew nuts, albeit at a relatively low occurrence. Circular dichroism indicated that Ana o 3 purified from raw and roasted cashew nuts had similar secondary structure, and dynamic light scattering analysis indicated there was no observable difference in particle size. The stability of Ana o 3 purified from raw and roasted cashew nuts to trypsin was similar in the absence of or following treatment with a reducing agent. Only minor differences in IgE binding to Ana o 3 were observed by ELISA among a cohort of cashew-allergic patient sera.