X-ray diffraction data were collected at the European Synchrotron Research Facility (ESRF; Grenoble, France) on the ID23-1 beamline at 100 K and images recorded on a Pilatus 6M detector (Dectris). Images were processed using the automatic data processing pipeline (GrenADES) based on XDS for indexing, scaling, etc. Data analysis was realized using the Phenix software suite. The structure of hBChE (PDB 1P0I) devoid of any ligand, glycan, or water molecules was used to determine the initial model by molecular replacement. Electron densities were observed in the active site gorge and allowed fitting of ligand. Ligand geometry restraints for the leaving group were processed using Phenix eLBOW and the semi-empirical quantum mechanical method (AM1). Each model was refined by iterative cycles of Phenix.refine and model building using Coot (Table ). Restraints for bond formation, angles and dihedrals were applied to account for the carbamoylation of Ser198. Human BChE structure, dimethylcarbamoylated at Ser198 and in complex with 5 (leaving group of 6), was deposited into the Protein Data Bank under accession number 8AI7.