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Vol: 188, No: 7, 2006; Pages: 2392–2399

Identification of a Novel -Galactosidase from the Hyperthermophilic Archaeon Sulfolobus solfataricus

Stan J. J. Brouns,1* Nicole Smits,1 Hao Wu,1 Ambrosius P. L. Snijders,2 Phillip C. Wright,2 Willem M. de Vos,1 and John van der Oost1

Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen
University, Hesselink van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands.


Sulfolobus solfataricus is an aerobic crenarchaeon that thrives in acidic volcanic pools. In this study, we have purified and characterized a thermostable -galactosidase from cell extracts of S. solfataricus P2 grown on the trisaccharide raffinose. The enzyme, designated GalS, is highly specific for -linked galactosides, which are optimally hydrolyzed at pH 5 and 90°C. The protein consists of 74.7-kDa subunits and has been identified as the gene product of open reading frame Sso3127. Its primary sequence is most related to plant enzymes of glycoside hydrolase family 36, which are involved in the synthesis and degradation of raffinose and stachyose. Both the galS gene from S. solfataricus P2 and an orthologous gene from Sulfolobus tokodaii have been cloned
and functionally expressed in Escherichia coli, and their activity was confirmed. At present, these Sulfolobus enzymes not only constitute a distinct type of thermostable -galactosidases within glycoside hydrolase clan D but also represent the first members from the Archaea.

Keywords:Sulfolobussolfataricus; -galactosidase;trisaccharideraffinose;orthologous gene;Sulfolobus tokodaii;Escherichia coli;Sulfolobus;Archaea;taxonomy.

Corresponding author: Tel 31-317-483110; Fax 31-317-483829.

E-mail: stan .brouns@wur.nl


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