Decarboxylation\nof the Catalytic Lysine Residue by\nthe C5α-Methyl-Substituted Carbapenem NA-1-157 Leads to Potent\nInhibition of the OXA-58 Carbapenemase

Antibiotic resistance in bacteria\nis a major global health\nconcern.\nThe wide spread of carbapenemases, bacterial enzymes that degrade\nthe last-resort carbapenem antibiotics, is responsible for multidrug\nresistance in bacterial pathogens and has further significantly exacerbated\nthis problem. Acinetobacter baumannii is one of the leading nosocomial pathogens due to the acquisition\nand wide dissemination of carbapenem-hydrolyzing class D β-lactamases,\nwhich have dramatically diminished available therapeutic options.\nThus, new antibiotics that are active against multidrug-resistantA. baumannii and carbapenemase inhibitors are urgently\nneeded. Here we report characterization of the interaction of the\nC5α-methyl-substituted carbapenem NA-1-157 with one of the clinically\nimportant class D carbapenemases, OXA-58. Antibiotic susceptibility\ntesting shows that the compound is more potent than commercial carbapenems\nagainst OXA-58-producingA. baumannii, with a clinically sensitive MIC value of 1 μg/mL. Kinetic\nstudies demonstrate that NA-1-157 is a very poor substrate of the\nenzyme due mainly to a significantly reduced deacylation rate. Mass\nspectrometry analysis shows that inhibition of OXA-58 by NA-1-157\nproceeds through both the classical acyl-enzyme intermediate and a\nreversible covalent species. Time-resolved X-ray crystallographic\nstudies reveal that upon acylation of the enzyme, the compound causes\nprogressive decarboxylation of the catalytic lysine residue, thus\nseverely impairing deacylation. Overall, this study demonstrates that\nthe carbapenem NA-1-157 is highly resistant to degradation by the\nOXA-58 carbapenemase.