The need to develop β-lactamase inhibitors against class C cephalosporinases of Gram-negative pathogens represents an urgent clinical priority. To respond to this challenge, five boronic acid derivatives, including a new cefoperazone analogue, were synthesized and tested against the class C cephalosporinase ofAcinetobacter baumannii [Acinetobacter-derived cephalosporinase (ADC)]. The commercially availablecarbapenem antibiotics were also assayed. In the boronic acid series, a chiral cephalothin analogue with ameta-carboxyphenyl moiety corresponding to the C3/C4 carboxylate of β-lactams showed the lowest Ki (11 (1 nM). In antimicrobial susceptibility tests, this cephalothin analogue lowered the ceftazidime and cefotaximeminimum inhibitory concentrations (MICs) of Escherichia coli DH10B cells carrying blaADC from 16 to 4 μg/mL and from 8 to 1 μg/mL, respectively. On the other hand, each carbapenem exhibited a Ki of <20 μM, andtimed electrospray ionization mass spectrometry (ESI-MS) demonstrated the formation of adducts correspondingto acyl-enzyme intermediates with both intact carbapenem and carbapenem lacking the C6hydroxyethyl group. To improve our understanding of the interactions between the β-lactamase and theinhibitors, we constructed models of ADC as an acyl-enzyme intermediate with (i) the meta-carboxyphenylcephalothin analogue and (ii) the carbapenems, imipenem and meropenem. Our first model suggests that thischiral cephalothin analogue adopts a novel conformation in the β-lactamase active site. Further, the additionof the substituent mimicking the cephalosporin dihydrothiazine ring may significantly improve affinity for theADCβ-lactamase. In contrast, theADC-carbapenem models offer a novel role for theR2 side group and alsosuggest that elimination of the C6 hydroxyethyl group by retroaldolic reaction leads to a significantconformational change in the acyl-enzyme intermediate. Lessons from the diverse mechanisms andstructures of the boronic acid derivatives and carbapenems provide insights for the development of newβ-lactamase inhibitors against these critical drug resistance targets.

Inhibition of the Class C β-Lactamase from Acinetobacter spp.: Insights into Effective Inhibitor Design / S. M., Drawz; M., Babic; C. R., Bethel; M., Taracila; A. M., Distler; Ori, Claudia; Caselli, Emilia; Prati, Fabio; R. A., Bonomo. - In: BIOCHEMISTRY. - ISSN 0006-2960. - STAMPA. - 49:(2010), pp. 329-340. [10.1021/bi9015988]

Inhibition of the Class C β-Lactamase from Acinetobacter spp.: Insights into Effective Inhibitor Design

ORI, CLAUDIA;CASELLI, Emilia;PRATI, Fabio;
2010

Abstract

The need to develop β-lactamase inhibitors against class C cephalosporinases of Gram-negative pathogens represents an urgent clinical priority. To respond to this challenge, five boronic acid derivatives, including a new cefoperazone analogue, were synthesized and tested against the class C cephalosporinase ofAcinetobacter baumannii [Acinetobacter-derived cephalosporinase (ADC)]. The commercially availablecarbapenem antibiotics were also assayed. In the boronic acid series, a chiral cephalothin analogue with ameta-carboxyphenyl moiety corresponding to the C3/C4 carboxylate of β-lactams showed the lowest Ki (11 (1 nM). In antimicrobial susceptibility tests, this cephalothin analogue lowered the ceftazidime and cefotaximeminimum inhibitory concentrations (MICs) of Escherichia coli DH10B cells carrying blaADC from 16 to 4 μg/mL and from 8 to 1 μg/mL, respectively. On the other hand, each carbapenem exhibited a Ki of <20 μM, andtimed electrospray ionization mass spectrometry (ESI-MS) demonstrated the formation of adducts correspondingto acyl-enzyme intermediates with both intact carbapenem and carbapenem lacking the C6hydroxyethyl group. To improve our understanding of the interactions between the β-lactamase and theinhibitors, we constructed models of ADC as an acyl-enzyme intermediate with (i) the meta-carboxyphenylcephalothin analogue and (ii) the carbapenems, imipenem and meropenem. Our first model suggests that thischiral cephalothin analogue adopts a novel conformation in the β-lactamase active site. Further, the additionof the substituent mimicking the cephalosporin dihydrothiazine ring may significantly improve affinity for theADCβ-lactamase. In contrast, theADC-carbapenem models offer a novel role for theR2 side group and alsosuggest that elimination of the C6 hydroxyethyl group by retroaldolic reaction leads to a significantconformational change in the acyl-enzyme intermediate. Lessons from the diverse mechanisms andstructures of the boronic acid derivatives and carbapenems provide insights for the development of newβ-lactamase inhibitors against these critical drug resistance targets.
49
329
340
Inhibition of the Class C β-Lactamase from Acinetobacter spp.: Insights into Effective Inhibitor Design / S. M., Drawz; M., Babic; C. R., Bethel; M., Taracila; A. M., Distler; Ori, Claudia; Caselli, Emilia; Prati, Fabio; R. A., Bonomo. - In: BIOCHEMISTRY. - ISSN 0006-2960. - STAMPA. - 49:(2010), pp. 329-340. [10.1021/bi9015988]
S. M., Drawz; M., Babic; C. R., Bethel; M., Taracila; A. M., Distler; Ori, Claudia; Caselli, Emilia; Prati, Fabio; R. A., Bonomo
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11380/639767
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