OatA

OatA, short for O-acetyltransferase A, is a gene found in several Gram-positive bacteria that encodes an enzyme responsible for the O-acetylation of peptidoglycan. The enzyme specifically transfers an acetyl group to the C-6 hydroxyl of N-acetylmuramic acid residues within the peptidoglycan layer, altering the chemical properties of the cell wall.

The OatA enzyme is typically associated with the cell wall or cytoplasmic membrane and is thought to act on newly synthesized or remodeling peptidoglycan. It uses acetyl-CoA as the acetyl donor in its reaction. O-acetylation of MurNAc reduces the susceptibility of peptidoglycan to lysozyme, an antimicrobial enzyme of the host innate immune system, by hindering the enzymatic cleavage of the glycosidic bond. As a result, oatA-mediated modification can enhance bacterial survival in hostile environments and, in some species, influence virulence traits.

OatA is notably described in pathogens such as Staphylococcus aureus and Listeria monocytogenes, among others. In these organisms, loss of oatA function typically increases lysozyme sensitivity and can attenuate virulence, underscoring a role in immune evasion. The distribution and regulation of oatA vary by species, with homologous O-acetyltransferases present in several Gram-positive bacteria. In some contexts, additional related enzymes (such as oatB) may contribute to similar peptidoglycan modifications.