ObjectiveThe biochemical properties of a putative thermostable cycloisomaltooligosaccharide (CI) glucanotransferase gene from Thermoanaerobacter thermocopriae were determined using a recombinant protein (TtCITase) expressed in Escherichia coli and purified to a single protein.ResultsThe 171-kDa protein displayed maximum activity at pH 6.0, and enzyme activity was stable at pH 5.0-11.0. The optimal temperature was 60 degrees C in 1h incubation, and thermal stability of the protein was 63% at 60 degrees C for 24h. TtCITase produced CI-7 to CI-17, as well as CI-18, CI-19, and CI-20, which are relatively large CIs. Additionally, an unusual kinetic feature of TtCITase was its negative cooperative behavior in the dextran T2000 cleavage reaction.ConclusionsBased on our results, TtCITase can be applied to produce relatively large CIs at high temperature.