What is "deamidation"

n. 1 (context biochemistry English) The conversion of glutamine, asparagine, glutamine residues in a polypeptide to glutamic acid or aspartic acid by treatment with strong acid, transamidase or deamidase. 2 (context organic chemistry English) Conversion of an amide to a carboxylic acid.

Deamidation is a chemical reaction in which an amide functional group is removed from an organic compound. In biochemistry, the reaction is important in the degradation of proteins because it damages the amide-containing side chains of the amino acids asparagine and glutamine.

In the biochemical deamidation reaction, the side chain of an asparagine attacks the following peptide group (in black at top right of Figure), forming a symmetric succinimide intermediate (in red). The symmetry of the intermediate results in two products of its hydrolysis, either aspartate (in black at left) or in isoaspartate, which is a beta amino acid (in green at bottom right). This process is considered a deamidation because the amide in the asparagine side chain is replaced by a carboxylate group. However, a similar reaction can occur in aspartate side chains, yielding a partial conversion to isoaspartate.