SER-HIS-ASP catalytic triad in model non-aqueous solvent environment: A computational study

Emerging new properties and applications of enzymes in organic solvents and ionic liquids are unabating. By applying a combined Quantum Mechanics/Continuum Mechanics computation on a prototypical catalytic triad serine-histidine-aspartate (SER-HIS-ASP) interacting with ethanol or acetonitrile molecules, the major difference between protic and aprotic solvents in effecting transition-state stabilization has been analyzed. Moderately polar aprotic solvent acetonitrile is predicted to be unable to stabilize the transition state in replacing the role of the oxyanion-hole environment, whereas protic ethanol solvent molecules of similar polarity to acetonitrile are adequate in re-gaining the enzymatic activities.