TABLE 1.

Classification of class B metallo-β-lactamases: subclass designations of representative metallo-β-lactamases and consensus sequences based on structural similarities to identified Zn2+ ligandsa

β-LactamaseSubstrate(s)Ligand(s)b
Zn1Zn2
116118196120/121221263
Subclass B1 (BcII, IMP-1, CcrA, VIM-2, SPM-1)Broad spectrumHisHisHisAsp/(Arg/Cys)CysHis
Subclass B2c (CphA, Sfh-1)Preferential hydrolysis of carbapenems(Asn)(His)(His)Asp/(Arg)CysHis
Subclass B3 (L1, FEZ-1, Gob-1, CAU-1)Preferential hydrolysis of cephalosporinsHis/GlnHisHisAsp/Hisd(Ser)His
  • a Data are from references 46, 50, and 51.

  • b Amino acids in parentheses do not appear to be active-site zinc ligands.

  • c Zn1 ligand for subclass B2 is inhibitory to enzymatic activity. The amino acids indicated have not been confirmed crystallographically to bind this Zn2+ atom.

  • d His121 replaces Cys221 as the second zinc ligand.