Pyrazolopyrimidines establish MurC as a vulnerable target in Pseudomonas aeruginosa and Escherichia coli

Area of Science:

• Microbiology
• Medicinal Chemistry
• Drug Discovery

Background:

• The bacterial peptidoglycan biosynthesis pathway is a validated target for antibiotics, with existing drugs like β-lactams and glycopeptides demonstrating clinical success.
• Mur ligases are crucial enzymes in synthesizing the N-acetyl-muramic acid-pentapeptide building block of peptidoglycan.
• MurC, the initial Mur ligase, catalyzes the ligation of L-alanine to UDP-N-acetylmuramic acid, a critical step in pentapeptide precursor synthesis.

Purpose of the Study:

• To identify and characterize novel inhibitors of the MurC enzyme.
• To evaluate the antibacterial activity of these inhibitors against key bacterial pathogens.
• To validate MurC as an essential target for novel antibacterial drug discovery.

Main Methods:

• Screening for pyrazolopyrimidine compounds with inhibitory activity against MurC enzymes from Escherichia coli and Pseudomonas aeruginosa.
• Assessing bactericidal activity against efflux-deficient bacterial strains.
• Utilizing radio-labeled precursor incorporation to confirm inhibition of peptidoglycan biosynthesis.
• Conducting genetic studies to confirm MurC as the specific target of the pyrazolopyrimidines.

Main Results:

• A novel class of pyrazolopyrimidines demonstrated subnanomolar potency against both E. coli and P. aeruginosa MurC.
• These compounds exhibited bactericidal activity against efflux-deficient strains.
• Evidence confirmed selective inhibition of peptidoglycan biosynthesis and identified MurC as the target.
• Low micromolar Minimum Inhibitory Concentrations (MIC) were observed against wild-type bacteria in the presence of permeability enhancers, highlighting permeability and efflux as challenges.

Conclusions:

• MurC is an essential enzyme for bacterial survival, validating it as an attractive target for antibacterial drug discovery.
• Pyrazolopyrimidines represent a promising new class of antibacterials with potent activity against MurC.
• Overcoming bacterial permeability and efflux mechanisms is crucial for the clinical efficacy of this chemical series.