The Journal of Biochemistry
Online ISSN : 1756-2651
Print ISSN : 0021-924X
β-Glycosidase from the Hyperthermophilic Archaeon Sulfolobus solfataricus: Structure and Activity in the Presence of Alcohols
Sabato D'AuriaRoberto NucciMose' RossiEnrico BertoliFabio TanfaniIgnacy GryczynskiHenry MalakJoseph R. Lakowiczx
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1999 Volume 126 Issue 3 Pages 545-552

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Abstract

β-Glycosidase from the extreme thermophilic archaeon Sulfolobus solfataricus is a tetrameric protein with a molecular mass of 240 kDa, stable in the presence of detergents, and with a maximal activity at temperatures above 95°C. Understanding the structureactivity relationships of the enzyme under different conditions is of fundamental importance for both theoretical and applicative purposes. In this paper we report the effect of methanol, ethanol, 1-propanol, and 1-butanol on the activity of S. solfataricus 6-glyco-sidase expressed in Escherichia coli. The alcohols stimulated the enzyme activity, with 1-butanol producing its maximum effect at a lower concentration than the other alcohols. The structure of the enzyme was studied in the presence of 1-butanol by circular dichroism, and Fourier-transform infrared and fluorescence spectroscopies. Circular dichroism and steady-state fluorescence measurements revealed that at low temperatures the presence of the alcohol produced no significant changes in the tertiary structure of the enzyme. However, time-resolved fluorescence data showed that the alcohol modifies the protein microenvironment, leading to a more flexible enzyme structure, which is probably responsible for the enhanced enzymatic activity.

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© The Japanese Biochemical Society
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