Generation of Aggregates of Lactalbumin by UVB Light Exposure [component]

Whey proteins are widely used as ingredients in the form of aggregates to obtain certain functionalities in food applications. The aim of this study was to understand how UV illumination generates aggregates of α-lactalbumin (-LA) as an alternative to heat treatments traditionally used for industrial production of protein aggregates. Absorption of UV light by -LA caused cleavage of disulfide bonds and release of thiol groups, which resulted in primarily disulfide-mediated aggregation. This
more » ... cess mediated efficient aggregation with up to 98% monomer conversion into aggregates through formation of intermolecular disulfide bonds, while only minor levels of nonreducible cross-links were observed. SDS-PAGE analysis revealed that illumination led to formation of dimeric, trimeric and oligomeric forms of -LA. LC-MS/MS analysis showed that all of the four native disulfide bonds in α-LA were cleaved by UV illumination but to different extents, and the extent of cleavage was found to be higher in the absence of calcium. Seventeen different non-native disulfides were formed after 24 h of UV illumination. Two di-tyrosine bonds were identified (Tyr103-Tyr103 and Tyr36-Tyr103) alongside di-tryptophan (Trp118-Trp118) and tyrosine-tryptophan (Tyr50-Trp60) cross-links. In addition,
doi:10.1021/acs.jafc.0c00757.s001 fatcat:cs4smjexgzgwnk4xmrzpyf5q34