Murein-degrading enzyme. May play a role in recycling of muropeptides during cell elongation and/or cell division (By similarity). Exolytic cleavage of the (1->4)-beta-glycosidic linkage between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues in peptidoglycan, from either the reducing or the non-reducing ends of the peptidoglycan chains, with concomitant formation of a 1,6-anhydrobond in the MurNAc residue. LysM domains are thought to be involved in peptidoglycan binding. Belongs to the transglycosylase Slt family. Was originally thought to be involved in hexaheme nitrite reductase (cytochrome c552) expression.