Three factors that modulate the activity of class D β-lactamases and interfere with the post-translational carboxylation of Lys70

The activity of class D beta-lactamases is dependent on Lys(70) carboxylation in the active site. Structural, kinetic and affinity studies show that this post-translational modification can be affected by the presence of a poor substrate such as moxalactam but also by the V117T substitution. Val(117) is a strictly conserved hydrophobic residue located in the active site. In addition, inhibition of class D beta-lactamases by chloride ions is due to a competition between the side chain carboxylate of the modified Lys(70) and chloride ions. Determination of the individual kinetic constants shows that the deacylation of the acyl-enzyme is the rate-limiting step for the wild-type OXA-10 beta-lactamase.