Meropenem inhibits D,D-carboxypeptidase activity in Mycobacterium tuberculosis.
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.
Tuberculosis Research Section, National Institute of Allergy and Infectious Disease, NIH, Bethesda, MD 20892, USA.
Pradeep
P
Kumar
Kriti
K
Arora
John R
JR
Lloyd
Ill Y
IY
Lee
Vinod
V
Nair
Elizabeth
E
Fischer
Helena I M
HI
Boshoff
Clifton E
CE
Barry
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects*; D006801:Humans; D000077731:Meropenem; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013845:Thienamycins / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D013845:Thienamycins; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D000077731:Meropenem