Enzyme catalysis in organic solvents

Abstract

Enzymes are powerful catalysts with many unique properties. With their high activity and (stereo) selectivity they have great potential for many applications as catalysts in organic synthesis. Especially after it was discovered that enzymes are not only active in water, but in organic solvents as well. This is interesting because of the higher solubility of many, possibly interesting, reaction compounds in organic solvents. Enzymes show, however, in an organic solvent a different behaviour then in water. They are in some solvents more stable, in some solvents less, they are less active in organic sol vents, they have a different activity in different solvents, and the water content of the organic sol vent plays a crucial role. In modern day literature it is believed that all this behaviour is caused by the influence of the solvent on the enzyme molecule, disturbing the active conformation. This work discusses the behaviour of enzymes in organic solvents and tries to explain this behaviour using a thermodynamical approach. Therefore basic information on thermodynamics and enzyme catalysis is provided. This thermodynamical approach leads to models that are capable of qualitative explanation of observed behaviour and prediction of enzyme behaviour in other solvents. In these models a solvent does not have a direct influence on the enzyme itself, only on the reaction mechanism. This is the basic difference to which this approach leads .