Thioredoxin treatment increases digestibility and lowers allergenicity of milk

Background: By resisting digestion in the stomach, the major bovine milk al lergen, beta-lactoglobulin, is believed to act as a transporter of vitamin A and retinol to the intestines. beta-Lactoglobulin has 2 intramolecular di sulfide bonds that may be responsible for its allergic effects. Objective: This study was carried out to assess the importance of disulfide bonds to the allergenicity and digestibility of beta-lactoglobulin, Methods: beta-Lactoglobulin was subjected to reduction by the ubiquitous pr otein thioredoxin, which was itself reduced by the reduced form of nicotina mide adenine dinucleotide phosphate by means of nicotinamide adenine dinucl eotide phosphate-thioredoxin reductase, Digestibility was measured with a s imulated gastric fluid; results were analyzed by SDS-PAGE, Allergenicity wa s assessed with an inbred colony of high IgE-producing dogs sensitized to m ilk. Results: As found for other proteins with intramolecular disulfide bonds,be ta-lactoglobulin was reduced specifically by the thioredoxin system, After reduction of one or both of its disulfide bonds, beta-lactoglobulin became strikingly sensitive to pepsin and lost allergenicity as determined by skin test responses and gastrointestinal symptoms in the dog model. Conclusion: The results provide new evidence that thioredoxin can be applie d to enhance digestibility and lower allergenicity of food proteins.