Predicting Enzyme Catalyzed Reaction Equilibria in Cosolvent-Water Mixtures as a Function of Ph and Solvent Composition

Abstract

Synthetic yields in enzymatic condensation reactions can often be improved by using organic solvents in monophasic systems. However, the addition of these cosolvents may result in loss of stability of the enzyme. Therefore, knowing that stabilization of the enzyme is necessary and often laborious, it would be useful to predict the potential improvement of the reaction equilibrium in the presence of the solvents before modifying the enzyme. This paper describes a model for predicting reaction equilibria in cosolvent-water mixtures by simply measuring the equilibrium in water, and the apparent pKa of all reactants in those mixtures. In the model a reference reaction must be chosen. This choice of reference reaction is crucial for the outcome of the model. The reference reaction should be chosen such that the same functional groups are present in the same ionic state both in the reactants as in the products. The model works quite well for the model system studied, i.e. synthesis of penicillin G from 6-aminopenicillanic acid and phenylacetic acid.