Escherichia coli murein-DD-endopeptidase insensitive to beta-lactam antibiotics

A novel endopeptidase degrading the peptide cross-links in sacculi has been isolated from Escherichia coli and purified to homogeneity. The enzyme has a molecular weight of 30,000 and, in contrast to already known enzymes of similar specificity, remains fully active in the presence of beta-lactam antibiotics. In addition, it is exceptional in being inhibited by single-stranded deoxyribonucleic acid and by some polynucleotides. The possible role of the enzyme in cell division is discussed.