Degradation mechanism for Zearalenone ring-cleavage by Zearalenone hydrolase RmZHD: A QM/MM study

The danger of zearalenone (ZEN) as an endocrine disruptor to humans and the environment has aroused increasing attention. In this study, we implemented the quantum mechanics/molecular mechanics (QM/MM) method to investigate the degradation mechanism of ZEN hydrolase (RmZHD) toward ZEN at the atomic level. The degradation process involves two concerted reaction pathways, where the active site contains a Ser-His-Glu triplet as a proton donor. With the Boltzmann-weighted average potential barriers of 18.1 and 21.5 kcal/mol, the process undergoes proton transfer and nucleophilic-substituted ring opening to form a hydroxyl product. Non-covalent interaction analyses elucidated hydrogen bonding between key amino acids with ZEN. The electrostatic influence analysis of 16 amino acids proposes residues Asp34 and His128 as the possible mutation target for future mutation design of enzyme RmZHD. An in-depth investigation of the protein environment of RmZHD can improve the bioremediation efficiency of endocrine disrupting chemicals.