Conserved ancillary residues situated proximally to the VIM-2 active-site affect its metallo β-lactamase activity.

Verona-integron-metallo-β-lactamase (VIM-2) is one of the most widespread class B β-lactamase responsible for β-lactam resistance. Although active-site residues help in metal binding, the residues nearing the active-site possess functional importance. Here, to decipher the role of such residues in the activity and stability of VIM-2, the residues E146, D182, N210, S207, and D213 were selected through in-silico analyses and substituted with alanine using site-directed mutagenesis.

Two non-active site residues W165 and L166 prominently influence the beta-lactam hydrolytic ability of OXA-23 beta-lactamase.

Dissemination of class D OXA-type carbapenemases is one of the significant causes of beta-lactam resistance in Gram-negative bacteria. The amino acid residues present near the active site are involved in hydrolytic mechanism of class D carbapenemases, though it is not identified in OXA-23. Here, with the help of site-directed mutagenesis, we aimed to explicate the importance of the residues W165, L166 and V167 of the possible omega loop and residue D222 in the short β5-β6 loop on the activity of OXA-23.