Structure difference of Jack bean urease and Helicobacter pylori urease on binding interactions with quercetin

Urease catalyzes the hydrolysis of urea to carbamate and ammonia, leading to nitrogen loss, environmental pollution, and health issues, so numerous compounds have been screened for urease inhibition using Jack bean urease (JBU) and H. pylori urease (HPU) without consideration their structure difference. Previous studies have shown that the same inhibitor can exhibit distinct inhibitory effects on JBU and HPU, but limited papers focus on the effects mechanism. In this study, we systematically investigated the thermodynamic and kinetic properties of JBU and HPU binding with quercetin, focusing on the structural effects on both commonly studied ureases. The results revealed that quercetin inhibited both JBU and HPU activities, with IC₅₀ values of 16.76 ± 0.77 μM and 36.17 ± 0.73 μM, respectively. Inhibition was identified as noncompetitive for JBU and mixed-competitive for HPU. Quercetin interacted with both JBU and HPU with quenching rate constants (K_q) of 3.72 ± 0.18 × 10¹³ M^-1 s^-1 for JBU and 0.28 ± 0.04 × 10¹³ M^-1 s^-1 for HPU. Molecular docking revealed that quercetin mainly bound to the flap region of JBU, inhibiting its function, and the JBU-quercetin complex had high binding stability and low binding free energy.