FIGURE 1.

Reaction scheme of class A β-lactamase. a, reaction scheme for hydrolysis of β-lactam antibiotics in the active site of class A β-lactamases. B represents the general base. Base1 and Base2 represent different residues for the acylation and deacylation step respectively. b, concerted base model for the acylation step of the catalytic cycle with substrate-induced proton transfer from Lys-73 to Glu-166 so that Lys-73 serves as the general base. The deacylation step employs Glu-166 as the general base. The dashed arrow represents intermediate steps between the pre- and post-deacylation complex.