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See detailEnantioselective synthesis of thioesters as substrates for high-through put screening assays of Penicillin Binding Proteins
Simon, Justine ULg; Zervosen, Astrid ULg; Bouillez, André ULg et al

Poster (2013, June 19)

Excessive utilization of beta-lactam antibiotics like penicillin has created drug-resistant strains in bacteria. One of the main mechanisms of resistance is the production of drug resistant Penicillin ... [more ▼]

Excessive utilization of beta-lactam antibiotics like penicillin has created drug-resistant strains in bacteria. One of the main mechanisms of resistance is the production of drug resistant Penicillin Binding Proteins (PBPs) and the over expression of these proteins. The transglycosidase and transpeptidase activities of PBPs catalyze the last two steps of peptidoglycan biosynthesis, which is unique to bacteria, and lies outside the cytoplasmic membrane. PBPs are interesting targets and efforts are still done to find new inhibitors. <br />A thioesterase activity has been described for various PBPs. For example, the thioester S2d is a substrate of PBP R39 of Actinomadura and of PBP2x of Streptococcus pneumoniae. The utilization of thioesters allows a rapid screening of active compounds in high-through put screening assays. Furthermore detailed kinetic studies using thioesters as reporter substrates are also possible. <br />Here we will present the enantioselective synthesis of the thioesters and their application as substrates in high through put screening assays. [less ▲]

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See detailSynthesis and evaluation of boronic acids as inhibitors of Penicillin Binding Proteins of classes A, B and C
Zervosen, Astrid ULg; Sauvage, Eric ULg; Bouillez, André ULg et al

Poster (2012, April 18)

The widespread use of beta-lactam antibiotics has lead to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to beta-lactams by three main mechanisms: the production of ... [more ▼]

The widespread use of beta-lactam antibiotics has lead to the worldwide appearance of drug-resistant strains. Bacteria have developed resistance to beta-lactams by three main mechanisms: the production of beta-lactamases that catalyze hydrolysis of beta-lactams, the production of low-affinity, drug resistant Penicillin Binding Proteins (PBPs) and the over expression of resistant PBPs. PBPs are interesting targets because they catalyse the last steps of the biosynthesis of peptidoglycan, which is unique in bacteria and has no mammalian analogs, outside the cytoplasmic membrane. Various non-ß-lactam inhibitors of PBPs have been developed with the objective of attempting to stall the development of ß-lactam resistance. Boronic acids are potent beta-lactamase inhibitors and have been shown to display some specificity for soluble transpeptidases and PBPs, but their potential as inhibitors of the latter enzymes is yet to be widely explored. Recently, a (2, 6-dimethoxybenzamido)methylboronic acid was identified as being a potent inhibitor of Actinomadura sp. R39 transpeptidase (IC50: 1.3 µM). Here, we will discuss the synthesis of a number of acylaminomethylboronic acids, analogs of (2, 6-dimethoxybenzamido)methylboronic acid, and their potential as inhibitors of PBPs. Several boronic acids of this library were able to inhibit PBPs of classes A, B and C from penicillin sensitive strains. Thus (2-nitrobenzamido)methylboronic acid was identified as a good inhibitor of class A PBP (PBP1b from S. pneumoniae, IC50 = 26 µM), class B PBP (PBP2xR6 from S. pneumoniae, IC50 = 138 µM) and class C PBP (R39 from Actinomadura sp., IC50 = 0.6 µM). Crystal structures of complexes of R39 and PBP1b with boronic acid analogs of our library have already been solved and allowed an interpretation of results. We believe that this work opens new avenues towards the development of molecules that will inhibit PBPs, and eventually display bactericidal effect, on distinct bacterial species. [less ▲]

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See detailSynthesis and evaluation of boronic acids as inhibitors of Penicillin Binding Proteins of classes A, B and C.
Zervosen, Astrid ULg; Bouillez, André ULg; Herman, Alexandre et al

in Bioorganic & Medicinal Chemistry (2012), 20(12), 3915-24

In response to the widespread use of beta-lactam antibiotics bacteria have evolved drug resistance mechanisms that include the production of resistant Penicillin Binding Proteins (PBPs). Boronic acids are ... [more ▼]

In response to the widespread use of beta-lactam antibiotics bacteria have evolved drug resistance mechanisms that include the production of resistant Penicillin Binding Proteins (PBPs). Boronic acids are potent beta-lactamase inhibitors and have been shown to display some specificity for soluble transpeptidases and PBPs, but their potential as inhibitors of the latter enzymes is yet to be widely explored. Recently, a (2,6-dimethoxybenzamido)methylboronic acid was identified as being a potent inhibitor of Actinomadura sp. R39 transpeptidase (IC(50): 1.3muM). In this work, we synthesized and studied the potential of a number of acylaminomethylboronic acids as inhibitors of PBPs from different classes. Several derivatives inhibited PBPs of classes A, B and C from penicillin sensitive strains. The (2-nitrobenzamido)methylboronic acid was identified as a good inhibitor of a class A PBP (PBP1b from Streptococcus pneumoniae, IC(50)=26muM), a class B PBP (PBP2xR6 from Streptococcus pneumoniae, IC(50)=138muM) and a class C PBP (R39 from Actinomadura sp., IC(50)=0.6muM). This work opens new avenues towards the development of molecules that inhibit PBPs, and eventually display bactericidal effects, on distinct bacterial species. [less ▲]

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See detailUnexpected tricovalent binding mode of boronic acids within the active site of a penicillin binding protein.
Zervosen, Astrid ULg; Herman, Raphaël ULg; Kerff, Frédéric ULg et al

in Journal of the American Chemical Society (2011)

Boronic acids bearing appropriate side chains are good inhibitors of serine amidohydrolases. The boron usually adopts a tetrahedral conformation, bound to the nucleophilic serine of the active site and ... [more ▼]

Boronic acids bearing appropriate side chains are good inhibitors of serine amidohydrolases. The boron usually adopts a tetrahedral conformation, bound to the nucleophilic serine of the active site and mimicking the transition state of the enzymatic reaction. We have solved the structures of complexes of a penicillin-binding protein, the DD-peptidase from Actinomadura sp. R39, with four amidomethylboronic acids (2,6 dimethoxybenzamidomethylboronic acid, phenylacetamidomethylboronic acid, 2-chlorobenzamidomethylboronic acid, and 2-nitrobenzamidomethylboronic acid) and the pinacol ester derived from phenylacetamidomethylboronic acid. We found that, in each case, the boron forms a tricovalent adduct with Ogamma of Ser49, Ser298, and the terminal amine group of Lys410, three key residues involved in the catalytic mechanism of penicillin-binding proteins. This represents the first tricovalent enzyme-inhibitor adducts observed by crystallography. In two of the five R39-boronate structures, the boronic acid is found as a tricovalent adduct in two monomers of the asymmetric unit and as a monocovalent adduct with the active serine in the two remaining monomers of the asymmetric unit. Formation of the tricovalent complex from a classical monocovalent complex may involve rotation around the Ser49 Calpha-Cbeta bond to place the boron in a position to interact with Ser298 and Lys410, and a twisting of the side chain amide such that its carbonyl oxygen is able to hydrogen bond to the oxyanion hole NH of Thr413. Biphasic kinetics were observed in three of the five cases and details of the reaction between R39 and 2,6-dimethoxybenzamidomethylboronic acid were studied. Observation of biphasic kinetics was not, however, thought to be correlated to formation of tricovalent complexes, assuming that the latter do form in solution. Based on the crystallographic and kinetic results, a reaction scheme for this unexpected inhibition by boronic acids is proposed. [less ▲]

Detailed reference viewed: 43 (10 ULg)