Lyses staphylococcal cells by hydrolyzing the polyglycine interpeptide bridges of the peptidoglycan. Hydrolysis of the -Gly-|-Gly- bond in the pentaglycine inter-peptide link joining staphylococcal cell wall peptidoglycans. Binds 1 zinc ion per subunit. Monomer. Belongs to the peptidase M23B family.