The mycotoxin zearalenone has been contaminating maize and other grains. It can be hydrolyzed and inactivated by the lactonase ZHD. Zearalenone differs from other quorum-sensing lactones. ZFR is a ligand product of hydrolysis. Macrolides are organic compounds containing a lactone ring of at least twelve members.
Title: The structure of a complex of the lactonohydrolase zearalenone hydrolase with the hydrolysis product of zearalenone at 1.60 A resolution Qi Q, Yang WJ, Zhou HJ, Ming DM, Sun KL, Xu TY, Hu XJ, Lv H Ref: Acta Crystallographica F Struct Biol Commun, 73:376, 2017 : PubMed
Zearalenone hydrolase (ZHD) is an alpha/beta-hydrolase that detoxifies and degrades the lactone zearalenone (ZEN), a naturally occurring oestrogenic mycotoxin that contaminates crops. Several apoenzyme and enzyme-substrate complex structures have been reported in the resolution range 2.4-2.6 A. However, the properties and mechanism of this enzyme are not yet fully understood. Here, a 1.60 A resolution structure of a ZHD-product complex is reported which was determined from a C-terminally His6-tagged ZHD crystal soaked with 2 mM ZEN for 30 min. It shows that after the lactone-bond cleavage, the phenol-ring region moves closer to residues Leu132, Tyr187 and Pro188, while the lactone-ring region barely moves. Comparisons of the ZHD-substrate and ZHD-product structures show that the hydrophilic interactions change, especially Trp183 N1, which shifts from contacting O2 to O12', suggesting that Trp183 is responsible for the unidirectional translational movement of the phenol ring. This structure provides information on the final stage of the catalytic mechanism of zearalenone hydrolysis.
