LD-carboxypeptidase activity in Escherichia coli. I. The LD-carboxypeptidase activity in ether treated cells.

The activities of the LD-carboxypeptidases of Escherichia coli K 12 and of a mutant strain 155 with reduced activities were studied with the aid of ether treated cells. Evidence was obtained that was consistent with the suggestion that in both strains two LD-carboxypeptidase activities are present. Activity I degrades the nucleotide activated precursor UDP-MurNAc-tetrapeptide and activity II splits off D-alanine residues from position 4 of the peptide subunits in the nascent murein. In the mutant strain activity I is reduced 10fold compared with strain K 12, whereas activity II is not affected. The two activities could be distinguished with regard to their sensitivity to D-amino acids and the beta-lactam antibiotic thienamycin.