Targeting β-Lactose with AA9 Lytic Polysaccharide Monooxygenase (LPMO) to Treat Lactose Intolerance: A Molecular Docking, DFT and Molecular Dynamic Simulation Study

The common metabolic disorder, lactose intolerance, is often treated with oral lactase enzyme supplements, which can frequently cause gastrointestinal instability. This work utilizes Malbranchea cinnamomea's AA9 lytic polysaccharide monooxygenase (LPMO) to target beta-lactose (β-lactose) in an investigation of a new enzymatic approach for lactose breakdown. Potential possibilities for lactose breakdown are AA9 LPMOs, copper-dependent enzymes that oxidatively cleave glycosidic bonds in polysaccharides. We employed a combined in silico method that incorporated molecular docking, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. Docking studies revealed that β-lactose formed hydrogen bonds with key residues ARG56 and ALA101, exhibiting a greater binding affinity (-5.2 kcal/mol) toward LPMO compared to the control citric acid (-4.9 kcal/mol). DFT analysis, showing excellent stability and appropriate reactivity for enzyme interaction. The higher stability of the LPMO-β-lactose complex was highlighted by MD simulation over 100 ns, which showed lower root mean square deviation (RMSD) and root mean square fluctuation (RMSF) values, greater structural compactness, and reduced solvent accessibility when compared to the control. These findings suggest that β-lactose can interact efficiently with the LPMO active site, thereby enhancing its potential as a novel enzymatic target for lactose breakdown and providing a viable platform for treating lactose intolerance.