Characterization, Structural Analysis, and Thermal Stability Mutation of a New Zearalenone-Degrading Enzyme Mined from <i>Bacillus subtilis</i>

Abstract

Zearalenone (ZEN) is a widespread mycotoxin that causes serious damage to animal husbandry and poses a threat to human health. A screen of ZEN-degrading soil bacteria yielded <i>Bacillus subtilis</i> YT-4, which yielded 80% ZEN degradation after 6 h and 95% after 36 h. The gene sequence encoding the degradative enzyme ZENY was mined from the genome of YT-4 and expressed in yeast. ZENY is an α/β-hydrolase with an optimal enzyme activity at 37 °C and pH 8. By breaking the lactone ring of ZEN, it produces ZENY-C₁₈H₂₄O₅ with a molecular weight of 320.16 g/mol. Sequence comparison and molecular docking analyses identified the catalytic ZENY triad 99S-245H-123E and the primary ZEN-binding mode within the hydrophobic pocket of the enzyme. To improve the thermal stability of the enzyme for industrial applications, we introduced a mutation at the N-terminus, specifically replacing the fifth residue N with V, and achieved a 25% improvement in stability at 45 °C. These findings aim to achieve ZEN biodegradation and provide insight into the structure and function of ZEN hydrolases.