References of "Fernandez, Maria Carmen"
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See detailCharacterization of the new AmpC beta-lactamase FOX-8 reveals a single mutation, Phe313Leu, located in the R2 loop that affects ceftazidime hydrolysis.
Perez-Llarena, Francisco Jose; Kerff, Frédéric ULg; Zamorano, Laura et al

in Antimicrobial agents and chemotherapy (2013), 57(10), 5158-61

A novel class C beta-lactamase (FOX-8) was isolated from a clinical strain of Escherichia coli. The FOX-8 enzyme possessed a unique substitution (Phe313Leu) compared to FOX-3. Isogenic E. coli strains ... [more ▼]

A novel class C beta-lactamase (FOX-8) was isolated from a clinical strain of Escherichia coli. The FOX-8 enzyme possessed a unique substitution (Phe313Leu) compared to FOX-3. Isogenic E. coli strains carrying FOX-8 showed an 8-fold reduction in resistance to ceftazidime relative to FOX-3. In a kinetic analysis, FOX-8 displayed a 33-fold reduction in kcat/Km for ceftazidime compared to FOX-3. In the FOX family of beta-lactamases, the Phe313 residue located in the R2 loop affects ceftazidime hydrolysis and alters the phenotype of E. coli strains carrying this variant. [less ▲]

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See detailDistant and new mutations in CTX-M-1 beta-lactamase affect cefotaxime hydrolysis.
Perez-Llarena, Francisco J; Kerff, Frédéric ULg; Abian, Olga et al

in Antimicrobial Agents and Chemotherapy (2011), 55(9), 4361-8

The CTX-M beta-lactamases are an increasingly prevalent group of extended-spectrum beta-lactamases (ESBL). Point mutations in CTX-M beta-lactamases are considered critical for enhanced hydrolysis of ... [more ▼]

The CTX-M beta-lactamases are an increasingly prevalent group of extended-spectrum beta-lactamases (ESBL). Point mutations in CTX-M beta-lactamases are considered critical for enhanced hydrolysis of cefotaxime. In order to clarify the structural determinants of the activity against cefotaxime in CTX-M beta-lactamases, screening for random mutations was carried out to search for decreased activity against cefotaxime, with the CTX-M-1 gene as a model. Thirteen single mutants with a considerable reduction in cefotaxime MICs were selected for biochemical and stability studies. The 13 mutated genes of the CTX-M-1 beta-lactamase were expressed, and the proteins were purified for kinetic studies against cephalothin and cefotaxime (as the main antibiotics). Some of the positions, such as Val103Asp, Asn104Asp, Asn106Lys, and Pro107Ser, are located in the (103)VNYN(106) loop, which had been described as important in cefotaxime hydrolysis, although this has not been experimentally confirmed. There are four mutations located close to catalytic residues-Thr71Ile, Met135Ile, Arg164His, and Asn244Asp-that may affect the positioning of these residues. We show here that some distant mutations, such as Ala219Val, are critical for cefotaxime hydrolysis and highlight the role of this loop at the top of the active site. Other distant substitutions, such as Val80Ala, Arg191, Ala247Ser, and Val260Leu, are in hydrophobic cores and may affect the dynamics and flexibility of the enzyme. We describe here, in conclusion, new residues involved in cefotaxime hydrolysis in CTX-M beta-lactamases, five of which are in positions distant from the catalytic center. [less ▲]

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