Laboratory Variants GES G170L , GES G170K , and GES G170H Increase Carbapenem Hydrolysis and Confer Resistance to Clavulanic Acid

The Guiana extended-spectrum (GES) β-lactamase GES G170H , GES G170L , and GES G170K mutants showed k cat , K m , and k cat / K m values very dissimilar to those of GES-1 and GES-5. The enhancement of the hydrolytic activity against carbapenems is potentially due to a shift of the substrate in the active site that provides better positioning of the deacylating water molecule caused by the presence of the imidazole ring of H170 and of the long side chain of K170 and L170.