TEMPERATURE-INDUCED DENATURATION OF BETA-GLYCOSIDASE FROM THE ARCHAEON SULFOLOBUS-SOLFATARICUS

Citation
S. Dauria et al., TEMPERATURE-INDUCED DENATURATION OF BETA-GLYCOSIDASE FROM THE ARCHAEON SULFOLOBUS-SOLFATARICUS, Journal of Biochemistry, 120(2), 1996, pp. 292-300
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0021-924X
Volume
120
Issue
2
Year of publication
1996
Pages
292 - 300
Database
ISI
SICI code
0021-924X(1996)120:2<292:TDOBFT>2.0.ZU;2-0
Abstract
The beta-glycosidase isolated from the extreme thermophilic archaeon S ulfolobus solfataricus, grown at 87 degrees C, is a tetrameric protein with a molecular mass of 240 kDa, This enzyme is barely active at 30 degrees C and has optimal activity, over 95 degrees C, at pH 6.5, Its thermal stability was investigated at pH 10.1 and 10.6 by means of fun ctional studies, circular dichroism and differential scanning calorime try. There was no evidence of thermal activation of the enzyme and the temperature-induced denaturation was irreversible and not well repres ented by the two-state transition model. A more complex process occurr ed, involving the dissociation and unfolding of subunits, and subseque nt nonspecific association and/or aggregation, Denaturation temperatur e was around 85 degrees C, depending on protein concentration. The den aturation enthalpy change was between 7,500 and 9,800 kJ . mol(-1), de pending on the pH. The collapse of the native structure around 85 degr ees C was confirmed by circular dichroism measurements and time-depend ent activity studies, Finally, preliminary investigations were perform ed on the recombinant enzyme expressed in Escherichia coli.