abstract
- High level resistance to vancomycin and other glycopeptide antibiotics requires the synthesis of peptidoglycan terminating in the depsipeptide D-Ala-D-lactate, rather the usual D-Ala-D-Ala. We report the purification and enzymatic characterization of two D-Ala ligases from Streptomyces toyocaensis NRRL 15009 which produces the glycopeptide antibiotic A47934. One of these enzymes catalyzes only D-Ala-D-Ala peptide formation and is recovered from mid-exponential phase cell cultures. The other enzyme is a D-Ala-D-lactate ligase which can be detected in actively antibiotic producing stationary phase cultures or mid-exponential phase cultures grown in the presence of A47934. These results imply that peptidoglycan components of S. toyocaensis NRRL 15009 change upon induction of antibiotic production and predict the existence of a VanX-like D-Ala-D-Ala DD-dipeptidase activity.