Zearalenone hydrolase (ZHD) is the only reported α/β-hydrolase that can detoxify zearalenone (ZEN). ZHD has demonstrated its potential as a treatment for ZEN contamination that will not result in damage to cereal crops. Recent researches have shown that the V153H mutant ZHD increased the specific activity against α-ZOL, but decreased its specific activity to β-ZOL. To understand whyV153H mutation showed catalytic specificity for α-ZOL, four molecular dynamics simulations combining with protein network analysis for wild type ZHD α-ZOL, ZHD β-ZOL, V153H α-ZOL, and V153H β-ZOL complexes were performed using Gromacs software. Our theoretical results indicated that the V153H mutant could cause a conformational switch at the cap domain (residues Gly161⁻Thr190) to affect the relative position catalytic residue (H242). Protein network analysis illustrated that the V153H mutation enhanced the communication with the whole protein and residues with high betweenness in the four complexes, which were primarily assembled in the cap domain and residues Met241 to Tyr245 regions. In addition, the existence of α-ZOL binding to V153H mutation enlarged the distance from the OAE atom in α-ZOL to the NE2 atom in His242, which prompted the side chain of H242 to the position with catalytic activity, thereby increasing the activity of V153H on the α-ZOL. Furthermore, α-ZOL could easily form a right attack angle and attack distance in the ZHD and α-ZOL complex to guarantee catalytic reaction. The alanine scanning results indicated that modifications of the residues in the cap domain produced significant changes in the binding affinity for α-ZOL and β-ZOL. Our results may provide useful theoretical evidence for the mechanism underlying the catalytic specificity of ZHD.
Keywords: alanine scanning; conformational change; molecular dynamics simulation; protein network analysis; zearalenone hydrolase.