Chemical shift perturbations induced by the acylation of Enterococcus faecium L,D-transpeptidase catalytic cysteine with ertapenem.

Penicillin-binding proteins were long considered as the only peptidoglycan cross-linking enzymes and one of the main targets of β-lactam antibiotics. A new class of transpeptidases, the L,D-transpeptidases, has emerged in the last decade. In most Gram-negative and Gram-positive bacteria, these enzymes generally have nonessential roles in peptidoglycan synthesis. In some clostridiae and mycobacteria, such as Mycobacterium tuberculosis, they are nevertheless responsible for the major peptidoglycan cross-linking pathway. L,D-Transpeptidases are thus considered as appealing new targets for the development of innovative therapeutic approaches. Carbapenems are currently investigated in this perspective as they are active on extensively drug-resistant M. tuberculosis and represent the only β-lactam class inhibiting L,D-transpeptidases. The molecular basis of the enzyme selectivity for carbapenems nevertheless remains an open question. Here we present the backbone and side-chain (1)H, (13)C, (15)N NMR assignments of the catalytic domain of Enterococcus faecium L,D-transpeptidase before and after acylation with the carbapenem ertapenem, as a prerequisite for further structural and functional studies.