Coordination and binding of ions in Ca 2+- and Ba 2+-containing methanol dehydrogenase and interactions with methanol

Abstract

Models representing the active sites of Ca 2+- and Ba 2+-containing methanol dehydrogenase (MDH) enzymes and their interaction with methanol are investigated using density functional theory methods and a continuum solvation model (PCM). Information on structure and energetics of such models in gas phase and implicit water solvent environments are obtained at the B3PW91/6-311+G ** theory levels. Solvent binding energy calculations of the ions indicate that Ca 2+ binding to the rest of the MDH active site model under consideration is 0.2–1.0 eV more stable than that of Ba 2+. Also the nature of the ion modifies the orientation and binding of the methanol to the MDH model. The hydroxyl oxygen (O16) of methanol is better coordinated with Ba 2+ than Ca 2+ in MDH models, which may make the initial proton abstraction during the methanol oxidation by MDH in Ba 2+-containing enzymes easier than that in Ca 2+-containing MDH enzymes.