Fig. 5

The classification of β-lactamases. Molecular structure classification using the Ambler method [16] and functional classification using the Bush-Jacobi-Medeiros method [17, 18] have both been employed. In the Ambler classification, β-lactamases are grouped into four classes A, B, C, and D by motifs composed of primary sequences constituting the protein molecules. β-lactamases of classes A, C, and D use a serine at the enzyme active center, whereas β-lactamases of class B use metal zinc ions. In functional classification using the Bush-Jacobi-Medeiros method, β-lactamases are classified into groups 1 to 3 depending on the degradation of β-lactam substrates and the effect of the inhibitor