Characterization of a beta-N-acetylglucosaminidase of Escherichia coli andelucidation of its role in muropeptide recycling and beta-lactamase induction

Using the known mapping position the gene encoding a beta -1,4-N-acetylgluc osaminidase needed for the degradation of muropeptides could be identified, nagZ encodes a cytosolic enzyme active on N-actylglucosamyl-beta -1,4-(1,6 )-anhydromuramic acid containing muropeptides. These degradation products o f the peptidoglycan are formed during the enlargement of the murein sacculu s as a consequence of a growth mechanism, which couples the controlled degr adation of the cell wall polymer with the insertion of new material. NagZ i s needed for the formation of monosaccharides from the released disaccharid es during the cytosolic steps of the muropeptide-recycling pathway. The for mation of intracellular 1,6-anhydro-N-acetylmuramyl-peptides is important f or the expression control of the inducible beta -lactamases of the AmpC typ e. A mutant lacking active NagZ cannot establish AmpC mediated beta -lactam resistance. The biochemical characterization of the enzyme showed its acti vity on different muropeptides and inhibitors of enzyme activity could be i dentified, This observation might be important for designing inhibitors of NagZ that could prevent the establishment of beta -lactam resistance of Ent erobacteria possessing inducible beta -lactamases.