A kinetic study of NMC-A β-lactamase, an Ambler class A carbapenemase also hydrolyzing cephamycins

In order to analyze its kinetic parameters, an Ambler class A carbapenemase NMC-A was purified. NMC-A demonstrated unusually strong hydrolytic activity towards imipenem and meropenem. Moreover, it hydrolyzed cephamycins with kcat values uncommonly high for this class of β-lactamases. Clavulanic acid and tazobactam had comparable inhibitory activity against NMC-A, whereas sulbactam was the least active inhibitor. Noticeably, NMC-A was more readily inhibited by brobactam. All these catalytic properties suggest that NMC-A possesses an original structure of its active site allowing hydrolysis of β-lactams usually stable to the hydrolytic activity of class A β-lactamases.