A KINETIC-STUDY OF NMC-A BETA-LACTAMASE, AN AMBLER CLASS-A CARBAPENEMASE ALSO HYDROLYZING CEPHAMYCINS

In order to analyze its kinetic parameters, an Ambler class A carbapen emase NMC-A was purified. NMC-A demonstrated unusually strong hydrolyt ic activity towards imipenem and meropenem. Moreover, it hydrolyzed ce phamycins with k(cat) values uncommonly high for this class of beta-la ctamases. Clavulanic acid and tazobactam had comparable inhibitory act ivity 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 structur e of its active site allowing hydrolysis of beta lactams usually stabl e to the hydrolytic activity of class A beta-lactamases.