Quantitative analysis of the metabolism of soluble cytoplasmic peptidoglycan precursors of glycopeptide-resistant enterococci

Mol Microbiol. 1996 Jul;21(1):33-44. doi: 10.1046/j.1365-2958.1996.00617.x.


Transposon Tn1546 from Enterococcus faecium BM4147 mediates high-level resistance to the glycopeptide antibiotics vancomycin and teicoplanin. Tn 1546 encodes a dehydrogenase (VanH) and a ligase (VanA) that synthesize D-alanyl-D-lactate (D-Ala-D-Lac), a D,D-dipeptidase (VanX) that hydrolyses D-Ala-D-Ala and a two-component regulatory system (VanR-VanS) that controls transcription of the vanHAX operon. Strains of Enterococcus faecalis harbouring various copy numbers of the vanRSHAX cluster were tested to determine if there was a correlation between the levels of resistance to glycopeptides, the levels of expression of the corresponding resistance genes and the relative proportions of the different cytoplasmic peptidoglycan precursors. Increased transcription of the vanHAX operon was associated with increased incorporation of D-Ala-D-Lac into peptidoglycan precursors to the detriment of D-Ala-D-Ala, and with a gradual increase in the vancomycin-resistance levels. More complete elimination of D-Ala-D-Ala-containing precursors was required for teicoplanin resistance. The VanY and VanZ proteins also encoded by Tn1546 were not effectors of the regulation of the vanHAX operon but contributed to vancomycin and teicoplanin resistance, respectively. Differences at the regulatory level accounted for phenotypic diversity in acquired glycopeptide resistance by production of D-lac-ending precursors.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Carbon-Oxygen Ligases*
  • Cytoplasm / metabolism
  • DNA Transposable Elements
  • Dipeptidases / genetics
  • Dipeptidases / metabolism
  • Drug Resistance, Microbial / genetics
  • Enterococcus / drug effects*
  • Enterococcus / genetics
  • Enterococcus / metabolism*
  • Enterococcus faecalis / drug effects
  • Enterococcus faecalis / genetics
  • Enterococcus faecalis / metabolism
  • Enterococcus faecium / drug effects
  • Enterococcus faecium / genetics
  • Enterococcus faecium / metabolism
  • Genes, Bacterial
  • Genetic Complementation Test
  • Glycopeptides / pharmacology*
  • Ligases / genetics
  • Ligases / metabolism
  • Multigene Family
  • Peptidoglycan / metabolism*
  • Plasmids / genetics
  • Protein Precursors / metabolism*
  • Serine-Type D-Ala-D-Ala Carboxypeptidase*
  • Solubility


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA Transposable Elements
  • Glycopeptides
  • Peptidoglycan
  • Protein Precursors
  • VanA ligase, Bacteria
  • VanH protein, Enterococcus faecium
  • Dipeptidases
  • Serine-Type D-Ala-D-Ala Carboxypeptidase
  • VanX dipeptidase
  • Ligases
  • Carbon-Oxygen Ligases