β-lactamases are divided into four classes by the Ambler classification system based on sequence similarity: serine β-lactamases of classes A, C and D, and class B, in which zinc ion(s) are involved in catalysis . Serine β-lactamases are believed to have evolved from the main targets of βlactam antibiotics, the penicillin binding proteins (PBPs), which catalyze the transpeptidation step in bacterial cell wall synthesis . PBPs are inhibited by β-lactams through formation of a stable acyl-enzyme . In class A, C and D β-lactamases, however, deacylation of the acyl-enzyme can occur efficiently, leading to the release of the hydrolyzed β-lactam ring and preventing PBP inhibition. Class A including the TEM, CTX-M, and KPC families, are currently the most widespread β-lactamases in the clinic .