In:
Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 59, No. 9 ( 2015-09), p. 5714-5720
Abstract:
Combinations of β-lactams with clavulanate are currently being investigated for tuberculosis treatment. Since Mycobacterium tuberculosis produces a broad spectrum β-lactamase, BlaC, the success of this approach could be compromised by the emergence of clavulanate-resistant variants, as observed for inhibitor-resistant TEM variants in enterobacteria. Previous analyses based on site-directed mutagenesis of BlaC have led to the conclusion that this risk was limited. Here, we used a different approach based on determination of the crystal structure of β-lactamase Bla MAb of Mycobacterium abscessus , which efficiently hydrolyzes clavulanate. Comparison of Bla MAb and BlaC allowed for structure-assisted site-directed mutagenesis of BlaC and identification of the G 132 N substitution that was sufficient to switch the interaction of BlaC with clavulanate from irreversible inactivation to efficient hydrolysis. The substitution, which restored the canonical SDN motif (SDG→SDN), allowed for efficient hydrolysis of clavulanate, with a more than 10 4 -fold increase in k cat (0.41 s −1 ), without affecting the hydrolysis of other β-lactams. Mass spectrometry revealed that acylation of BlaC and of its G 132 N variant by clavulanate follows similar paths, involving sequential formation of two acylenzymes. Decarboxylation of the first acylenzyme results in a stable secondary acylenzyme in BlaC, whereas hydrolysis occurs in the G 132 N variant. The SDN/SDG polymorphism defines two mycobacterial lineages comprising rapidly and slowly growing species, respectively. Together, these results suggest that the efficacy of β-lactam–clavulanate combinations may be limited by the emergence of resistance. β-Lactams active without clavulanate, such as faropenem, should be prioritized for the development of new therapies.
Type of Medium:
Online Resource
ISSN:
0066-4804
,
1098-6596
DOI:
10.1128/AAC.00598-15
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2015
detail.hit.zdb_id:
1496156-8
SSG:
12
SSG:
15,3
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