D-alanine--D-alanine ligase (<db_xref db="EC" dbkey="6.3.2.4"/>) is a bacterial enzyme involved in cell-wall biosynthesis.It participates in forming UDP-N-acetylmuramyl pentapeptide, the peptidoglycan precursor.These enzymes are proteins of 300 to 360 amino acids containing many conserved regions. The N-terminal Gly-rich region could be involved in ATP-binding [<cite idref="PUB00000444"/>].