Deamidation is a chemical reaction in which an amide functional group in the side chain of the amino acids asparagine or glutamine is removed or converted to another functional group. Typically, asparagine is converted to aspartic acid or isoaspartic acid. Glutamine is converted to glutamic acid or pyroglutamic acid (5-oxoproline). In a protein or peptide, these reactions are important because they may alter its structure, stability or function and may lead to protein degradation. The net chemical change is the addition of a water group and removal of an ammonia group, which corresponds to a +1 (0.98402) Da mass increase. Although deamidation occurs on glutamine, glycosylated asparagine and other amides, these are negligible under typical proteolysis conditions.

Reference
Wiki: Deamidation

    Mycobacteria assemble a complex cell wall with cross-linked peptidoglycan (PG) which plays an essential role in maintenance of cell wall integrity and tolerance to osmotic pressure. We previously demonstrated that various hydrolytic enzymes are required to remodel PG during essential processes such as cell elongation and septal hydrolysis. Here, we explore the chemistry associated with PG cross-linking, specifically the requirement for amidation of the D-glutamate residue found in PG precursors.

Reference
Pubmed: Shaku MT, Ocius KL, Apostolos AJ, Pires MM, VanNieuwenhze MS, Dhar N, Kana BD. Amidation of glutamate residues in mycobacterial peptidoglycan is essential for cell wall cross-linking. Front Cell Infect Microbiol. 2023 Aug 24;13:1205829. doi: 10.3389/fcimb.2023.1205829.