Quinazolinone derivatives are important nitrogen-containing heterocycles widely used in antitumor agents and functional materials, but their conventional synthesis often relies on noble-metal catalysts and inefficient multistep processes with considerable environmental costs. In this study, we developed a QM/MM hybrid simulation and experimental validation framework to investigate the synergistic catalytic mechanism of an enzyme–Mn system for quinazolinone synthesis and to clarify how metal pre-activation and enzymatic microenvironment jointly regulate the reaction pathway and transition-state stability. Density functional theory, QM/MM calculations, and molecular dynamics simulations were integrated to quantify geometric configuration, charge distribution, solvation effects, substrate binding, and transition-state evolution in the catalytic process. The results showed that Mn-assisted enzyme catalysis reduced the activation energy by 36.5% compared with the enzyme-only system, while the predicted transition-state infrared frequencies deviated by less than 8 cm −1 from experimental measurements and the overall computational error remained below 2.5%. In addition, optimization of Mn charge states substantially improved catalyst cyclability, with an approximately sevenfold enhancement in reuse performance. These findings demonstrate that the synergistic effect between Mn-mediated substrate pre-activation and the enzymatic hydrogen-bond network is the key factor underlying efficient quinazolinone formation, and they provide a reliable theoretical basis for the design of noble-metal-free hybrid catalytic systems for sustainable synthesis.
Haotian Cao (Fri,) studied this question.