Activator of the cell wall hydrolases AmiA and AmiB. Required for septal murein cleavage and daughter cell separation during cell division. In vitro, exhibits weak endoproteolytic activity on beta-casein. Localizes at the septal ring. The coiled-coil domain is necessary and sufficient for recruitment to the divisome. The LytM domain is required for proper septal peptidoglycan splitting. Mutants show defects in septation and separation, and form very long filaments (1.5-fold increase). The phenotype is exacerbated when combined with nlpD (over 8-fold longer), more exacerbated with a triple mepM (yebA) or ygeR disruption (15-fold longer) and further yet by the quadruple disruption mutant (envC-nlpD-mepM(yebA)-ygeR, over 21-fold longer). Quadruple mutants are less sensitive to ampicillin lysis. Belongs to the peptidase M23B family. Was originally thought to have murein hydrolase activity. Unlike many members of this family does not have peptidase activity. Extended N-terminus.