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Angew Chem Int Ed Engl. 2019 Feb 11;58(7):1990-1994. doi: 10.1002/anie.201809424. Epub 2019 Jan 21.

Non-Hydrolytic β-Lactam Antibiotic Fragmentation by l,d-Transpeptidases and Serine β-Lactamase Cysteine Variants.

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Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK.
School of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK.


Enzymes often use nucleophilic serine, threonine, and cysteine residues to achieve the same type of reaction; the underlying reasons for this are not understood. While bacterial d,d-transpeptidases (penicillin-binding proteins) employ a nucleophilic serine, l,d-transpeptidases use a nucleophilic cysteine. The covalent complexes formed by l,d-transpeptidases with some β-lactam antibiotics undergo non-hydrolytic fragmentation. This is not usually observed for penicillin-binding proteins, or for the related serine β-lactamases. Replacement of the nucleophilic serine of serine β-lactamases with cysteine yields enzymes which fragment β-lactams via a similar mechanism as the l,d-transpeptidases, implying the different reaction outcomes are principally due to the formation of thioester versus ester intermediates. The results highlight fundamental differences in the reactivity of nucleophilic serine and cysteine enzymes, and imply new possibilities for the inhibition of nucleophilic enzymes.


antibiotic resistance; fragmentation; hydrolases; transpeptidases; β-lactamases

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