Spectroscopic studies of stability of papain in aqueous organic solvents

The effects of different concentrations of the water-miscible organic solvents ethanol, 1,4-dioxane. tetrahydrofuran (THF) and acetonitrile (ACN) on the stability of papain in aqueous Solution were studied. Papain exhibited high stability in aqueous ACN. ethanol and 1,4-dioxane. Decreases in the activity of the enzyme were observed at organic solvent concentrations above 60%. THF caused a dramatic reduction in activity even at low concentrations (5-10%). The solvent-induced structural changes were followed by means of circular dichroism (CD) and intrinsic fluorescence spectroscopy measurements. The decreases in enzyme activity at 90% THF or 90% 1,4-dioxane were accompanied by the loss of the tertiary structure. However, at 90% ethanol and 90% ACN, papain exhibited air increased amount of the alpha-helical conformation. with little change in the tertiary structure. (c) 2006 Elsevier B.V. All rights reserved.