Mechanisms of plastein formation influence the IgE-binding activity of egg white protein hydrolysates after simulated static digestion

Abstract

Egg is the second most common food allergen among infants and young children. This work investigated the influence of plastein reaction on immunoglobulin E (IgE)-binding activities of egg white protein hydrolysates after simulated gastrointestinal (GIT) digestion. Compared to hydrolysate precursors, the IgE-binding activity of Pepsin-Plastein significantly decreased from 35 ± 7% to 8 ± 2% (P < 0.05), and Papain-Plastein from 70 ± 5% to 59 ± 4%. Further GIT hydrolysis of Pepsin-Plastein maintained the reduced IgE-binding activity (7 ± 3%) whereas Papain-Plastein digestion restored the IgE-binding reactivity to 66 ± 7%. This discrepancy is related to the different mechanisms of plastein formation. Covalent modifications (decreased free amino nitrogen and sulfhydryl contents) provided biostability for Pepsin-Plastein, whereas hydrophobic interactions (increased surface hydrophobicity) mainly contributed to Papain-Plastein formation. The latter can be destroyed during GIT digestion leading to re-exposure of hidden IgE-binding epitopes. Taken together, plastein reaction is a promising strategy for inducing structural modifications that reduce the immune reactivity of allergenic proteins.