Studies on the Reactions of Biapenem with VIM Metallo β-Lactamases and the Serine β-Lactamase KPC-2

Carbapenems are important antibacterials and are both substrates and inhibitors of some beta-lactamases. We report studies on the reaction of the unusual carbapenem biapenem, with the subclass B1 metallo-beta-lactamases VIM-1 and VIM-2 and the class A serine-beta-lactamase KPC-2. X-ray diffraction studies with VIM-2 crystals treated with biapenem reveal the opening of the beta-lactam ring to form a mixture of the (2S)-imine and enamine complexed at the active site. NMR studies on the reactions of biapenem with VIM-1, VIM-2, and KPC-2 reveal the formation of hydrolysed enamine and (2R)- and (2S)-imine products. The combined results support the proposal that SBL /MBLmediated carbapenem hydrolysis results in a mixture of tautomerizing enamine and (2R)- and (2S)-imine products, with the thermodynamically favoured (2S)-imine being the major observed species over a relatively long-time scale. The results suggest that prolonging the lifetimes of beta-lactamase carbapenem complexes by optimising tautomerisation of the nascently formed enamine to the (2R)-imine and likely more stable (2S)-imine tautomer is of interest in developing improved carbapenems.

Automated summary

This study investigated the reaction of the carbapenem biapenem with different subclasses of beta-lactamases. The results showed the formation of enamine and various types of imine products. The findings support the idea that prolonging the lifetime of beta-lactamase carbapenem complexes by optimizing the tautomerization process could lead to improved carbapenems.