Benzoate catalysis in the hydrolysis of endo-5-[4'(5')imidazolyl]-bicyclo[2.2.1]hept-endo- 2-yl trans-cinnamate: Implications for the charge-transfer mechanism of catalysis by serine proteases.

The acceleration, by a factor of 2500, of the hydrolysis of endo-5-[4'(5')imidazolyl]bicyclo[2.2.1]hept-endo- 2-yl trans-cinnamate by 0.5 M sodium benzoate in 42 mol% dioxane in water can be explained without resort to operation of a "charge-relay" mechanism similar to that often postulated to account for the enzymatic activity of serine proteases. The degree of ionization of 4-methylimidazole and of sodium benzoate in 42 mol% dioxane in water at 60 degrees C have been measured by NMR spectroscopy.