Cell-wall hydrolase involved in septum cleavage during cell division. Can also act as powerful autolysin in the presence of murein synthesis inhibitors. Hydrolyzes the link between N-acetylmuramoyl residues and L-amino acid residues in certain cell-wall glycopeptides. Present throughout the periplasm in non-dividing cells, but localizes almost exclusively to a ring at the site of constriction in dividing cells. N-terminal domain is required and sufficient for targeting to the septal ring. Exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Can also be exported by the Sec system. Mutants are growing in chains of 3 to 6 cells. Belongs to the N-acetylmuramoyl-L-alanine amidase 3 family. Extended N-terminus.