Synthèse et caractérisation de composés à potentiel antimicrobien à base de peptides et de sulfahydantoïnes inhibitrices de B-lactamases

Authors: Paquet-Côté, Pierre-Alexandre
Advisor: Voyer, Normand
Other Title(s): Synthèse et caractérisation de composés à potentiel antimicrobien à base de peptides et de sulfahydantoïnes inhibitrices de bêta-lactamases
Synthèse et caractérisation de composés à potentiel antimicrobien à base de peptides et de sulfahydantoïnes inhibitrices de β-lactamases
Abstract: Antibiotic resistance is one of the top worldwide healthcare problems. Bacteria are continuously finding new ways to survive the treatment we develop. To stay ahead in this race, we must accelerate the development of new drugs that counteract bacterial resistance. The present study is divided in two projects each using a separate approach aiming to find new antimicrobial molecules. The first part of this thesis focusses on the study of antimicrobial peptides as a potential new class of antibiotics. Their mode of action is different than commercially available antibiotics and is less prone to induce resistance development. However, the design of new peptides for clinical uses is challenging because of the complexity of these compounds. To have a better understanding of the molecular determinants affecting their interaction with cellular membranes, we have developed a simple synthetic model peptide with a neutral global charge named 14-mer. Multiple analogs were synthesized bearing cationic amino acids at different positions in the sequence. Notably, analogs R4R11 and R5R10, bearing arginine residues at positions 4 and 11, and 5 and 10 respectively, were studied alongside the 14-mer model by various spectroscopic, biophysical and bioinformatics methods. These experiments show that the secondary structure and supramolecular self-assembly can be modulated by the position of the cationic residue in the peptide sequence. The peptide secondary structure affects their interactions with model membranes and living cells. The β-strand peptides tend to interact more selectively toward prokaryotic model membranes and cell whereas α-helical peptides interact indistinctly with both prokaryotic and eukaryotic model membranes and cells. In addition, a difference in peptide orientation has been observed between uncharged and cationic α-helical peptides when they interact with phospholipid membranes. These peptides have generally a higher affinity with thinner bilayers, and cationic peptides possess better interaction with cationic membranes. The investigation was continued by studying the effect of the incorporation of a molecular tag that is known to have a high affinity toward prokaryotic membranes. This was achieved by adding a bis-dipicolylamine (bis-DPA) ligand at the N-terminus of peptides 14-mer, R4R11 and R5R10 to form a Zn(II) complex in situ. The Zn(II) complex tends to increase the selectivity of the studied peptides toward prokaryotic model membranes and cells. The second part of this thesis instead focusses on finding new β-lactamase inhibitors in order to reduce the antibiotic resistance of one of the most versatile antibiotic families, the β-lactams. As potential candidates, the sulfahydantoin family has never been investigated for this application even if they possess similar structure to β-lactam antibiotics and has been shown to inhibit similar enzymes like proteases. To evaluate their potential, we synthesized multiple analogs containing the sulfahydantoin heterocycle starting from amino acids. These analogs were tested as inhibitors of two of the most prevalent β-lactamases, TEM-1 and TEM-15. Out of these compounds, two analogs have shown substantial inhibition with IC₅₀ values between 130 and 510 μM and inferred Kᵢ values between 32 and 55 μM. These results suggest that sulfahydantoin compounds have a good potential for the development of new and improved β-lactamase inhibitors.
Document Type: Thèse de doctorat
Issue Date: 2022
Open Access Date: 16 May 2022
Grantor: Université Laval
Collection:Thèses et mémoires

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