We report studies of the enzymatic activity of subtilisin Carlsberg (SC) in different solvents and pH's using two Substrates. From the Michaelis-Menten mechanism. we found the specificity constant (k(eat)/K-M) of enzymatic activity to be retarded when organic solvents. such as acetonitrile or dioxane, are added to the aqueous medium or when the pH is lowered. In order to address the role of solvation. we also studied the femtosecond dynamics of the enzyme and the solubility of substrates and products. We elucidate the nature of the free energy surface from the knowledge of the free energy change (K-M), catalytic turn over (k(eat)), solvation, and effect of pH on the enzymatic activity. (C) 2004 Elsevier B.V All rights reserved.