Open AccessVal‐237 for Ala substitution in the TEM‐2 β‐lactamase dramatically alters the catalytic efficiencies towards carbenicillin and ticarcillin
Author(s) -
Barthélémy Michel,
Péduzzi Jean,
Rowlands David,
Paul Gérard,
Moreau Gilles,
Labia Roger
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06788.x
Subject(s) - carbenicillin , ticarcillin , chemistry , mutant , hydrolysis , escherichia coli , biochemistry , enzyme , stereochemistry , ampicillin , antibiotics , antibiotic resistance , imipenem , gene
The mutant 554 of TEM‐2 β‐lactamase was selected for a decrease in the resistance to carbenicillin of an Escherichia coli K12 carrier. The amino acid sequence of the mutant β‐lactamase was determined by manual Edman degradation analysis of proteolytic peptides. A single substitution Val for Ala was localized at position 237. The mutant exhibited only 2% of the catalytic efficiency of the wild‐type enzyme towards carbenicillin and ticarcillin, whereas it retained 30–60% of the hydrolytic activity towards other penicillin and cephalosporin substrates. Carfecillin, the phenyl ester of the side‐chain carboxyl group of carbenicillin, was hydrolysed as a good substrate. This suggests that the behaviour of the mutant enzyme towards carbenicillin may result from ionic rather than steric constraints. A molecular model of the Val‐237 TEM‐2 mutant suggests possible electrostatic interaction between Glu‐171 and the carboxylic group of the side chain of carbenicillin.