Improvement of Digestibility of Bovine Serum Albumin by Chemical Treatment and Reduction in the Antigenicity of the Digests.

Abstract

Bovine serum albumin (BSA) was chemically treated in the presence or absence of L-cysteine (Cys) after the cleavage of hydrogen bonds by urea and reduction of disulfide linkages by sodium tetrahydroborate. The reduced BSA was re-oxidized with hydrogen peroxide and Cys treated- or non-Cys treated- BSA was obtained (C-BSA or NC-BSA). The percentage of thiol groups modified in C-BSA was 73.6%. The peptic digestibility of BSA was markedly improved by chemical treatment in the presence of Cys. The pancreatic and tryptic digestibility of BSA was higher in the order of C-BSA>NC-BSA>native BSA. SDS-PAGE confirmed that chemical treatment with Cys improved the digestibility of BSA and facilitated protein fragmentation into small molecular weight peptides by protease. Further, enzyme-linked immunosorbent assay showed that the antigenicity of the tryptic digests of BSA was reduced about one-tenth by the chemical treatment with Cys. This result indicated that the change in conformation of BSA decreased the antigenicity through enhancement of protease susceptibility.