The Enzymatic Activity of Inosine 5'-Monophosphate Dehydrogenase May Not Be a Vulnerable Target for Staphylococcus...

Area of Science:

• Microbiology
• Drug Discovery
• Biochemistry

Background:

• Inosine 5 -monophosphate dehydrogenase (IMPDH) is essential for bacterial pathogens like Staphylococcus aureus.
• Targeting IMPDH presents a potential strategy for novel antibiotic development.
• Previous IMPDH inhibitors showed limited antibacterial efficacy despite high selectivity.

Purpose of the Study:

• To develop potent and selective inhibitors of Staphylococcus aureus IMPDH (SaIMPDH) with antibacterial activity.
• To investigate the role of SaIMPDH enzymatic activity in S. aureus infection models.

Main Methods:

• Structure-informed design was employed to create SaIMPDH inhibitors.
• Inhibitor efficacy was assessed through minimal inhibitory concentration (MIC) determination and in vivo infection models.
• Inhibitor resistance was generated in vitro, and resistance mutations were characterized.

Main Results:

• Several novel SaIMPDH inhibitors demonstrated potent antibacterial activity (MIC < 2 μM) and low mammalian cytotoxicity.
• Inhibitor-resistant S. aureus strains emerged rapidly, with mutations in the SaIMPDH cofactor/inhibitor binding site.
• Resistant strains exhibited reduced inhibitor binding and catalytic activity but maintained virulence, and catalytically inactive IMPDH showed only mild virulence defects.

Conclusions:

• While structure-informed design yielded potent SaIMPDH inhibitors, rapid resistance development and virulence data question the enzyme's enzymatic activity as a sole therapeutic target.
• The findings suggest that non-enzymatic functions of SaIMPDH may be critical for its role in S. aureus pathogenesis.
• Further research is needed to explore alternative strategies for targeting SaIMPDH or other pathways in S. aureus infections.