Novel strategies for inhibiting SufA protease: the role of ester substituents and biological properties.

Abstract

Aims: This study aims to develop novel antibacterial agents by targeting SufA protease, a key virulence factor in Finegoldia magna, using 1-aminoalkylphosphonate (1-AAP) diaryl esters as inhibitors.

Materials & methods: Structural optimization of a reference inhibitor, Cbz-6-AmNpthP(OC₆H₅)₂, was performed by introducing substituents at the para position of phenyl rings: -SCH₃ (8a), -OCH₃ (8b), and -COOCH₃ (8c). Enzymatic assays, molecular modeling, antibacterial activity screening, and CD spectroscopy were utilized to evaluate inhibitory potency, binding interactions, functional effects, and DNA interaction.

Results: Compound 8a demonstrated moderate SufA inhibition (k₂/K_i = 1500 M^{- 1} s^{- 1}), supported by molecular modeling that showed stable binding via hydrogen bonding and π-π stacking. It also protected host defense molecules (fibrinogen, LL-37) and exhibited broad-spectrum antibacterial activity (IC₅₀ = 0.02 µM against S. marcescens and F. magna). Compound 8c, despite weak SufA inhibition, displayed potent antibacterial activity (IC₅₀ < 0.01 µM), surpassing gentamicin.

Conclusions: 1-AAP derivatives, particularly 8a and 8c, exhibit promising antibacterial properties. These findings validate SufA as a therapeutic target and support further development of peptide-based inhibitors to enhance efficacy and selectivity.