Electrostatic interactions influence diazabicyclooctane inhibitor potency against OXA-48-like β-lactamases

Area of Science:

• Biochemistry and Molecular Biology
• Antimicrobial Resistance
• Structural Biology

Background:

• Carbapenemase-producing Enterobacterales are a significant threat to public health, complicating treatment of multi-drug resistant bacterial infections.
• OXA-48 carbapenemase is a prevalent enzyme conferring resistance to carbapenem antibiotics.
• Diazabicyclooctane (DBO) inhibitors like avibactam and nacubactam are crucial for overcoming β-lactamase-mediated resistance.

Purpose of the Study:

• To investigate the inhibitory mechanisms of avibactam and nacubactam against OXA-48 and its variants (OXA-163, OXA-405).
• To elucidate the structural basis for differential inhibition, particularly the role of the β5-β6 loop.
• To understand how sequence variations in OXA-48-like enzymes affect inhibitor reactivity.

Main Methods:

• Enzyme inhibition assays to determine the potency of avibactam and nacubactam against OXA-48, OXA-163, and OXA-405.
• X-ray crystallography and molecular dynamics simulations to visualize and analyze enzyme-inhibitor interactions.
• Mass spectrometry to investigate the desulfation of bound DBOs by the enzymes.

Main Results:

• Nacubactam showed significantly lower potency against OXA-48 compared to avibactam, a difference that diminished with OXA-163 and OXA-405.
• Structural analysis revealed electrostatic repulsion between Arg214 in OXA-48 and nacubactam, which was absent in OXA-163 and OXA-405 due to the lack of Arg214.
• All tested enzymes were found to desulfate bound DBOs, indicating a common inactivation pathway.

Conclusions:

• The presence of Arg214 in the OXA-48 β5-β6 loop is a key determinant of differential DBO inhibitor potency.
• Sequence variations in OXA-48-like β-lactamases can alter their interaction with inhibitors, influencing therapeutic efficacy.
• Understanding these structure-activity relationships is vital for developing next-generation carbapenemase inhibitors.