A mechanistic study on different metal-substituted forms of the Metallo-β-Lactamase NDM-1

PALACIOS, ANTONELA; LLARRULL, L; A. J. VILA

Encuentro; IV Latin American Meeting on Biological Inorganic Chemistry - V WOQUIBIO; 2014

The β-lactam antibiotic family represents the largest class of commercial antibiotics clinically used to treat Gram-negative and Gram-positive infections.1 β-Lactam antibiotics work by inhibiting cell wall synthesis. This class of antibiotics includes penicillin derivatives (penams), cephalosporins (cephems), monobactams and carbapenems. In particular, carbapenems comprise the latest generation of β-lactam antibiotics, used as last resort drugs to treat infections caused by resistant bacteria. The expression of β-lactamases is the most widely spread resistance mechanism displayed by bacteria. β-Lactamases are hydrolytic enzymes that selectively hydrolyze the four-membered β-lactam ring, rendering the antibiotic ineffective against their natural targets. There are four classes of β-lactamases: classes A, C, and D include enzymes with a serine in the active site, while class B enzymes are metal-dependent and hence called Metallo-β-Lactamases (MβLs). MβLs are divided into three subclasses, B1, B2, and B3.2 The class-B enzymes are of particular interest and concern given their ability to hydrolyze and provide resistance to virtually all classes of β-lactams antibiotics. Among them, NDM-1 is one of the most potent and widespread carbapenemases, raising an increasing clinical concern.3 NDM-1 belongs to subclass B1, is carried on a transmissible plasmid and has two Zn(II) ions in its active site. No clinical useful MβLs? inhibitor exists to date and unveiling the catalytic mechanism of MβLs is a prerequisite for the design of inhibitors or new β-lactam antibiotics. Here we report a mechanistic study by steady-state and pre-steady state kinetics on substrate hydrolysis by Zn(II), Co(II), and Cd(II)-NDM-1.