ABSTRACT
Indeed, water is a safe, harmless, and environmentally benign solvent. In addition, from practical and synthetic standpoints, the benefits of using water are immediately obvious, as it is unnecessary to dry solvents and substrates for reactions in aqueous media, and aqueous solutions of substrates or hydrated substrates can be used directly without further drying. Moreover, water has unique physical and chemical properties such as high dielectric constant and high cohesive energy density compared with most organic solvents. These properties allow highly efficient and selective enzymatic reactions to be conducted in living systems under mild conditions. Notably, the medium of enzymatic reactions is water, which plays major roles in the reactions. If the unique nature of water could be exploited
in vitro
as it is
in vivo
, it would be possible to develop interesting reactions with unique reactivity and selectivity that cannot be attained with organic solvents.
