The replacement of main cap domain to improve the activity of a ZEN lactone hydrolase with broad substrate spectrum

Zearalenone (ZEN) and its derivatives is a major kind of mycotoxins that being commonly detected in contaminated grain products. ZEN lactone hydrolase (ZHD) can hydrolyze ZEN to produce non-toxic product, providing an environment-friendly way for ZENs detoxification. However, most of ZEN derivatives are more toxic, which leads to a high demand for the novel ZHD with high degradation activity towards ZEN derivatives. Here, a new ZEN lactone hydrolase Zhd11B from Fonsecaea monophora was characterized to efficiently hydrolyze ZEN and more toxic derivatives α-ZAL and β-ZAL. The broad substrate spectrum of Zhd11B may attribute to the improved protein flexibility. Through cap-domain swap, the activity towards ZEN, α-ZAL and β-ZAL was further improved by 1.5-, 1.6- and 2.9-fold, respectively, which suggested that the conserved cap domain could be a structural element for ZHDs engineering, providing a new strategy for molecular modification of ZHDs. Structure comparison and molecular dynamic analysis showed that the protonation of catalytic histidine residue (H245 in Zhd11B) and a more stable combination between “goalkeeper” of the catalytic pocket are main determinant factors of ZHDs’ catalytic efficiency. Our results provide a good experimental material for better understanding of the mechanism of substrate specificity and cap domain swapping would provide a new strategy for the molecular modification.