Binding of β-Lactam Antibiotics to a Bioinspired Dizinc Complex Reminiscent of the Active Site of Metallo-β-lactamases

Abstract

Metallo-β-lactamases (mβls) cause bacterial resistance toward a broad spectrum of β-lactam antibiotics by catalyzing the hydrolytic cleavage of the four-membered β-lactam ring, thus inactivating the drug. Minutiae of the mechanism of these enzymes are still not well understood, and reports about binding studies of the substrates to the enzymes as well as to synthetic model systems are rare. Here we report a new pyrazolate-based bioinspired dizinc complex (1) reminiscent of the active site of binuclear mβls. Since 1 does not mediate hydrolytic degradation of β-lactams, the binding of a series of common β-lactam antibiotics (benzylpenicillin, cephalotin, 6-aminopenicillanic acid, ampicillin) as well as the inhibitor sulbactam and the simplest β-lactam, 2-azetidinone, to the dizinc core of 1 could now be studied in detail by NMR and IR spectroscopy as well as mass spectrometry. X-ray crystallographic information was obtained for 1 and its complexes with 2-azetidinone (2) and sulbactam (3); the latter represents the first structurally characterized dizinc complex with a bound β-lactam drug. While 2-azetidinone was found deprotonated and bridging in the clamp of the two zinc ions in 2, in 3 and all other cases the substrates preferentially bind via their carboxylate group within the bimetallic pocket. The relevance of this binding mode for mβls and consequences for the design of functional model systems are discussed.

Modelling Binuclear Metallobiosites: Insights from Pyrazole‐Supported Biomimetic and Bioinspired Complexes

“…Solid state structural investigations of β‐lactam binding have also been performed through co‐crystallization studies 40,59,60. The simplest β‐lactam, 2‐azetidinone, afforded N ‐deprotonated lactamido‐bridged structures in the cases of complexes 2 and 5 , and also more recently in the case of complex 17 (Scheme ) 59,60.…”

Metallo‐β‐lactamases and Their Biomimetic Complexes

“…[12,13,33,35,92,93,95,99,100,[111][112][113] In addition, the study of dicobalt(II) and dicadmium(II) systems in our work have paralleled the use of these metal ions for the crystallographic, spectroscopic, and kinetic investigations of the MβLs. [12,13,33,35,92,93,95,99,100,[111][112][113] In addition, the study of dicobalt(II) and dicadmium(II) systems in our work have paralleled the use of these metal ions for the crystallographic, spectroscopic, and kinetic investigations of the MβLs.…”

“…Ligands 1-6 were reported by Mugesh et al [13,95,96] and were used to generate dinuclear and mononuclear zinc(II) complexes; mononuclear complexes were obtained by treating ligands 1, 3, 4, and 5 with zinc(II) chloride. [99] The same group reported the four ligands 13-16, which are based on the same pyrazolate backbone, but vary in the side arm length and amine donor type. Reaction of zinc(II) acetate with 2 and 4 yielded dinuclear acetate-bridged complexes.…”

“…[106,107] The role of the metal-ionbound hydroxide moiety as the active nucleophile was established in these studies with an acceleration rate of about 10 7 reported in the case of the copper(II) complex of penicillin G. [104][105][106] In addition, the coordination of the metal ion through the β-lactam nitrogen atom and the carboxylate group was demonstrated. [109,110] There are a number of studies and reviews of both monoand dinuclear zinc(II) complexes as β-lactamase models; [12,13,33,35,90,92,93,95,99,100,[111][112][113][114][115] a selection of dinuclear Zn II MβL bioinspired complexes is shown in Figure 7, and representative kinetic data are listed in Table 2. [109,110] There are a number of studies and reviews of both monoand dinuclear zinc(II) complexes as β-lactamase models; [12,13,33,35,90,92,93,95,99,100,[111][112][113][114][115] a selection of dinuclear Zn II MβL bioinspired complexes is shown in Figure 7, and representative kinetic data are listed in Table...…”

“…Release of the product occurs after protonation at the β-lactam nitrogen atom. [99] Employing 1 H NMR spectroscopy and a reverse-phase HPLC method, Mugesh et al investigated the β-lactamase activity of BcII from B. cereus and complexes H to K. The NH groups of penicillin G and oxacillin were employed as probes in the 1 H NMR spectroscopic experiments. [92] Copyright 2000 American Chemical Society.…”