title: Inhibition of the broad spectrum nonmetallocarbapenamase of class A (NMC-A) beta-lactamase from Enterobacter cloacae by monocyclic beta-lactams.
abstract: beta-Lactamases hydrolyze beta-lactam antibiotics, a reaction that destroys their antibacterial activity. These enzymes, of which four classes are known, are the primary cause of resistance to beta-lactam antibiotics. The class A beta-lactamases form the largest group. A novel class A beta-lactamase, named the nonmetallocarbapenamase of class A (NMC-A) beta-lactamase, has been discovered recently that has a broad substrate profile that included carbapenem antibiotics. This is a serious development, since carbapenems have been relatively immune to the action of these resistance enzymes. Inhibitors for this enzyme are sought. We describe herein that a type of monobactam molecule of our design inactivates the NMC-A beta-lactamase rapidly, efficiently, and irreversibly. The mechanism of inactivation was investigated by solving the x-ray structure of the inhibited NMC-A enzyme to 1.95 A resolution. The structure shed light on the nature of the fragmentation of the inhibitor on enzyme acylation and indicated that there are two acyl-enzyme species that account for enzyme inhibition. Each of these inhibited enzyme species is trapped in a distinct local energy minimum that does not predispose the inhibitor species for deacylation, accounting for the irreversible mode of enzyme inhibition. Molecular dynamics simulations provided evidence in favor of a dynamic motion for the acyl-enzyme species, which samples a considerable conformational space prior to the entrapment of the two stable acyl-enzyme species in the local energy minima. A discussion of the likelihood of such dynamic motion for turnover of substrates during the normal catalytic processes of the enzyme is presented.
authors.affiliation: Groupe de Cristallographie Biologique, Institut de Pharmacologie et de Biologie Structurale du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Mourey
authors.forename: L P
authors.initials: LP
authors.lastname: Kotra
authors.forename: J
authors.initials: J
authors.lastname: Bellettini
authors.forename: A
authors.initials: A
authors.lastname: Bulychev
authors.forename: M
authors.initials: M
authors.lastname: O'Brien
authors.forename: M J
authors.initials: MJ
authors.lastname: Miller
authors.forename: S
authors.initials: S
authors.lastname: Mobashery
authors.forename: J P
authors.initials: JP
authors.lastname: Samama
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D016972:Enterobacter cloacae / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D011487:Protein Conformation; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; C088657:NmcA protein, Enterobacter cloacae; D001618:beta-Lactamases