A Kinetic Study of the Replacement by Site Saturation Mutagenesis of Residue 119 in NDM-1 Metallo-β-Lactamase.

New Delhi metallo-β-lactamase 1 (NDM-1) is a subclass B1 metallo-β-lactamase that exhibits a broad spectrum of activity against β-lactam antibiotics. Here we report the kinetic study of 6 Q119X variants obtained by site-directed mutagenesis of NDM-1. All Q119X variants were able to hydrolyze carbapenems, penicillins and first-, second-, third-, and fourth-generation cephalosporins very efficiently. In particular, Q119E, Q119Y, Q119V, and Q119K mutants showed improvements in kcat/Km values for penicillins, compared with NDM-1. The catalytic efficiencies of the Q119K variant for benzylpenicillin and carbenicillin were about 65- and 70-fold higher, respectively, than those of NDM-1. The Q119K and Q119Y enzymes had kcat/Km values for ceftazidime about 25- and 89-fold higher, respectively, than that of NDM-1.