Cell-wall hydrolase involved in septum cleavage during cell division. Hydrolyzes the link between N-acetylmuramoyl residues and L-amino acid residues in certain cell-wall glycopeptides. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the N-acetylmuramoyl-L-alanine amidase 3 family.