Fig. 5: Reaction sub-steps of the water assisted reaction.

a The initial structure, known as the „open” form of the water assisted reaction. b Schematic and NBO computational structure of the first water assisted proton transfer step, which is the result of orbital overlapping between the LP(3):O_H2O and the σ*(1):N^δ_Asn-H_H2O orbitals. c Schematic and NBO computational structure of the water assisted proton transfer. In this mechanism a significant orbital overlapping occur between the LP(3):O_H2O and the σ*(1):N^δ_Asn-H_H2O orbitals and between the LP(3):O_H2O and the σ*(1):N_Gly-H_Gly orbitals. d A representative schematic and NBO computational molecular structure of the second phase of the water assisted proton transfer step. Overlap occurs between the LP(2) N_Gly and the σ*(1) O_H2O-H_Gly orbitals. e The transition state formed by overlapping the LP(2):O_H2O and the σ*(1):N^δ_Asn-H_H2O orbitals and the LP(2):O^δ_Asn and the σ*(1):C^γ_Asn-N^δ_Asn orbitals. f The ring-closure step takes place with orbital overlapping between the LP(3):O^δ_Asn and the σ*(1):C^γ_Asn-N_Gly orbitals. g Schematic and NBO computational structure of the final ammonia release step. Orbital overlapping occur between the LP(3):O^δ_Asn and the σ*(1):C^γ_Asn-N^δ_Asn orbitals.