Structural effects of protein aging: terminal marking by deamidation in human triosephosphate isomerase.
Deamidation, the loss of the ammonium group of asparagine and glutamine to form aspartic and glutamic acid, is one of the most commonly occurring post-translational modifications in proteins.Since deamidation rates are encoded in the protein structure, it has been proposed that they can serve as molecular clocks for the timing of biological process