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Mol Microbiol. 2012 Oct;86(2):367-81. doi: 10.1111/j.1365-2958.2012.08199.x. Epub 2012 Aug 28.

Meropenem inhibits D,D-carboxypeptidase activity in Mycobacterium tuberculosis.

Author information

1
Tuberculosis Research Section, National Institute of Allergy and Infectious Disease, NIH, Bethesda, MD 20892, USA.

Abstract

Carbapenems such as meropenem are being investigated for their potential therapeutic utility against highly drug-resistant tuberculosis. These β-lactams target the transpeptidases that introduce interpeptide cross-links into bacterial peptidoglycan thereby controlling rigidity of the bacterial envelope. Treatment of Mycobacterium tuberculosis (Mtb) with the β-lactamase inhibitor clavulanate together with meropenem resulted in rapid, polar, cell lysis releasing cytoplasmic contents. In Mtb it has been previously demonstrated that 3-3 cross-linkages [involving two diaminopimelate (DAP) molecules] predominate over 4-3 cross-linkages (involving one DAP and one D-alanine) in stationary-phase cells. We purified and analysed peptidoglycan from Mtb and found that 3-3 cross-linkages predominate throughout all growth phases and the ratio of 4-3/3-3 linkages does not vary significantly under any growth condition. Meropenem treatment was accompanied by a dramatic accumulation of unlinked pentapeptide stems with no change in the tetrapeptide pools, suggesting that meropenem inhibits both a D,D-carboxypeptidase and an L,D-transpeptidase. We purified a candidate D,D-carboxypeptidase DacB2 and showed that meropenem indeed directly inhibits this enzyme by forming a stable adduct at the enzyme active site. These results suggest that the rapid lysis of meropenem-treated cells is the result of synergistically inhibiting the transpeptidases that introduce 3,3-cross-links while simultaneously limiting the pool of available substrates available for cross-linking.

PMID:
22906310
PMCID:
PMC3468717
DOI:
10.1111/j.1365-2958.2012.08199.x
[Indexed for MEDLINE]
Free PMC Article

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