Antigenicities of stem bromelain. Contribution of three-dimensional structure and individual amino acid residues.
The contribution of three-dimensional structure and individual amino acid residues to the antigenicities of macromolecular protein was investigated for a thiol protease stem bromelain as antigen. The extent of the participation was demonstrated by a decrease in antigenicity when the enzyme was denatured in 8 M urea before and after reductive cleavage of intrapeptide disulfide bonds or modified in particular amino acid residues. The results showed that the enzyme treated with 8 M urea without reductive cleavage of disulfide bonds preserved about 90% of antigenicity to antibodies against native stem bromelain, while the enzyme denatured after the reductive cleavage of disulfide bonds brought about almost 80% disappearance of the antigenicity. Modification of individual amino acid side chains revealed that lysine was the most immunodominant amino acid, showing 2.5% contribution per residue, and tyrosine followed with 1.2%. However, acidic amino acids such as flutamic and aspartic acids were found to be as low as 0.3%, and tryptophan was 0.2%. These data suggest that most of the antigenic determinants of stem bromelain are of the steric conformation in which lysine and/or tyrosine are most frequently involved as immunodominant amino acids.
D000596:Amino Acids / Q000032:analysis / Q000276:immunology; D000906:Antibodies / Q000032:analysis; D001963:Bromelains / Q000276:immunology*; D055598:Chemical Phenomena; D002621:Chemistry; D000939:Epitopes; D007074:Immunoglobulin G / Q000032:analysis; D011487:Protein Conformation; D011489:Protein Denaturation
D000596:Amino Acids; D000906:Antibodies; D000939:Epitopes; D007074:Immunoglobulin G; D001963:Bromelains