AcmA, the major autolysin ofLactococcus lactisMG1363 is a modular protein consisting of an N-terminal active site domain and a C-terminal peptidoglycan-binding domain. The active site domain is homologous to that of muramidase-2 of Enterococcus hirae, however, RP-HPLC analysis of muropeptides released fromBacillus subtilispeptidoglycan, after diges-tion with AcmA, shows that AcmA is an N-acetylglucosaminidase.