A gene, cgtA, encoding an extremely thermostable cyclodextrin glycosyltransferase (CGTase) was cloned from a thermophilic anaerobe, Thermoanaerobacter sp. ATCC 53627, and expressed in Escherichia coli. DNA and protein sequencing revealed that the mature enzyme of 683 amino acid residues (MW 75 kDa) was preceded by a signal peptide of 27 amino acid residues. The sequence of the Thermoanaerobacter CGTase was similar to sequences of Bacillus CGTases, with more than 58% identity, and very similar (89% identity) to a CGTase enzyme from Thermoanaerobacterium thermosulfurogenes.