beta-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus: Structure and activity in the presence of alcohols

beta-Glycosidase from the extreme thermophilic archaeon Subfolobus solfatar icus is a tetrameric protein with a molecular mass of 240 kDa, stable in th e presence of detergents, and with a maximal activity at temperatures above 95 degrees C, Understanding the structure-activity relationships of the en zyme under different conditions is of fundamental importance for both theor etical and applicative purposes. In this paper we report the effect of meth anol, ethanol, 1-propanol, and 1-butanol on the activity of S, solfataricus beta-glycosidase expressed in Escherichia coli, The alcohols stimulated th e enzyme activity, with 1-butanol producing its maximum effect at a lower c oncentration than the other alcohols. The structure of the enzyme was studi ed in the presence of 1-butanol by circular dichroism, and Fourier-transfor m infrared and fluorescence spectroscopies. Circular dichroism and steady-s tate fluorescence measurements revealed that at low temperatures the presen ce of the alcohol produced no significant changes in the tertiary structure of the enzyme. However, time-resolved fluorescence data showed that the al cohol modifies the protein microenvironment, leading to a more flexible enz yme structure, which is probably responsible for the enhanced enzymatic act ivity.