A Theoretical DFT Investigation of the Lysozyme Mechanism. Computational Evidence for a Covalent Intermediate Pathway

A theoretical DFT(B3LYP) investigation of the catalytic cycle of lysozyme has provided further evidence for a mechanism involving a glycosilenzyme covalent intermediate, in agreement with recent experimental data. This type of intermediate has been located along two different pathways. Along the favored path the retention of the anomeric configuration of the peptidoglycan NAM unit involved in the reaction, is the result of two subsequent inversions at the C, carbon. The other path involves the opening of the pyranose ring and a nucleophilic attack on the prochiral carbonyl group of the open aldehyde, restoring the original anomeric configuration. No evidence has been found for a pathway characterized by the formation of an oxocarbenium ion (stabilized by resonance and electrostatic interactions), as suggested in the most popular mechanistic schemes.