Mechanistic Insights into ?-Lactamase-Catalysed Carbapenem Degradation Through Product Characterisation.

ABSTRACT: ?-Lactamases are a major threat to the clinical use of carbapenems, which are often antibiotics of last resort. Despite this, the reaction outcomes and mechanisms by which ?-lactamases degrade carbapenems are still not fully understood. The carbapenem bicyclic core consists of a ?-lactam ring fused to a pyrroline ring. Following ?-lactamase-mediated opening of the ?-lactam, the pyrroline may interconvert between an enamine (2-pyrroline) form and two epimeric imine (1-pyrroline) forms; previous crystallographic and spectroscopic studies have reported all three of these forms in the contexts of hydrolysis by different ?-lactamases. As we show by NMR spectroscopy, the serine ?-lactamases (KPC-2, SFC-1, CMY-10, OXA-23, and OXA-48) and metallo-?-lactamases (NDM-1, VIM-1, BcII, CphA, and L1) tested all degrade carbapenems to preferentially give the ?² (enamine) and/or (R)-?¹ (imine) products. Rapid non-enzymatic tautomerisation of the ?² product to the (R)-?¹ product prevents assignment of the nascent enzymatic product by NMR. The observed stereoselectivity implies that carbapenemases control the form of their pyrroline ring intermediate(s)/product(s), thereby preventing pyrroline tautomerisation from inhibiting catalysis.

SUBMITTER: Lohans CT 

PROVIDER: S-EPMC6754457 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature