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Publication Abstract from PubMed

The emergence of class D beta-lactamases with carbapenemase activity presents an enormous challenge to health practitioners, particularly with regard to the treatment of infections caused by Gram-negative pathogens such as Acinetobacter baumanii. Unfortunately, class D beta-lactamases with carbapenemase activity are resistant to beta-lactamase inhibitors. To better understand the details of the how these enzymes bind and hydrolyze carbapenems, we have determined the structures of two deacylation-deficient variants (K84D and V130D) of the class D carbapenemase OXA-24 with doripenem bound as a covalent acyl-enzyme intermediate. Doripenem adopts essentially the same configuration in both OXA-24 variant structures, but varies significantly when compared to the non-carbapenemase class D member OXA-1/doripenem complex. The alcohol of the 6alpha hydroxyethyl moiety is directed away from the general base carboxy-K84, with implications for activation of the deacylating water. The tunnel formed by the Y112/M223 bridge in the apo form of OXA-24 is largely unchanged by the binding of doripenem. The presence of this bridge, however, causes the distal pyrrolidine/sulfonamide group to bind in a drastically different conformation compared to doripenem bound to OXA-1. The resulting difference in the position of the side-chain bridge sulfur of doripenem is consistent with the hypothesis that the tautomeric state of the pyrroline ring contributes to the different carbapenem hydrolysis rates of OXA-1 and OXA-24. These findings represent a snapshot of a key step in the catalytic mechanism of an important class D enzyme, and might be useful for the design of novel inhibitors.

Structures of the Class D Carbapenemase OXA-24 from Acinetobacter baumannii in Complex with Doripenem.,Schneider KD, Ortega CJ, Renck NA, Bonomo RA, Powers RA, Leonard DA J Mol Biol. 2011 Jan 6. PMID:21215758^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.