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Michel Barthélémy, Jean Péduzzi, David Rowlands, Gérard Paul, Gilles Moreau, Roger Labia, Val-237 for Ala substitution in the TEM-2 β-lactamase dramatically alters the catalytic efficiencies towards carbenicillin and ticarcillin, FEMS Microbiology Letters, Volume 117, Issue 3, April 1994, Pages 333–339, https://doi.org/10.1111/j.1574-6968.1994.tb06788.x
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Abstract
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.
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