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Immunochemical and structural analysis of pepsin-digested egg white ovomucoid
J Kovacs-Nolan1, J W Zhang, S Hayakawa
1Department of Food Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Journal of Agricultural and Food Chemistry
|January 16, 2001
Summary
Pepsin digestion of ovomucoid, an egg white protein, yielded fragments that retained IgE-binding activity. Reducing disulfide bonds in ovomucoid enhanced its digestibility and reduced allergenicity.
Area of Science:
- Food science
- Protein chemistry
- Allergenicity research
Background:
- Ovomucoid is a major allergen in egg white, contributing to food allergies.
- Understanding ovomucoid's structure and digestion is crucial for developing hypoallergenic egg products.
Purpose of the Study:
- To investigate the effects of pepsin digestion on ovomucoid structure and allergenicity.
- To identify pepsin-digested ovomucoid fragments and assess their IgE-binding activity.
- To explore the role of disulfide bonds in ovomucoid's resistance to digestion.
Main Methods:
- Pepsin digestion of ovomucoid
- Anion-exchange and reverse-phase HPLC for fragment isolation
- SDS-PAGE, N- and C-terminal sequencing for fragment identification
- ELISA for IgE-binding activity assessment
- Preparation of reduced carboxymethylated ovomucoid
Main Results:
- Four distinct ovomucoid fragments were identified after pepsin digestion, with molecular weights of 24, 18, 14 kDa, and a smaller peptide.
- All identified fragments exhibited IgE-binding activity in sera from egg-allergic individuals.
- Pepsin digestion did not significantly alter ovomucoid's trypsin inhibitor activity.
- Reduction of disulfide bonds in ovomucoid significantly increased its digestibility by pepsin.
Conclusions:
- Pepsin digestion yields fragments of ovomucoid that retain allergenicity.
- Disulfide bonds contribute significantly to ovomucoid's resistance to digestion.
- Reducing ovomucoid's disulfide bonds enhances digestibility and may reduce allergenicity.