抄録
An amylolytic enzyme, designated as PFTA (Pyrococcus furiosus thermostable amylolytic enzyme), was cloned from Pyrococcus furiosus and expressed in Escherichia coli. The recombinant PFTA was extremely thermostable, with an optimal temperature of 90°C. PFTA hydrolyzed maltooligosaccharides and starch to mainly produce maltotriose and maltotetraose. Also, the enzyme was capable of degrading pullulan and β-cyclodextrin, which are generally resistant to the attack of α-amylase. The major products from these substrates (pullulan and β-cyclodextrin) were mostly panose and maltoheptaose, respectively. These results verified that PFTA possesses novel catalytic characteristics of both α-amylase and cyclodextrin-hydrolyzing enzymes. Interestingly, this enzyme showed a unique hydrolytic activity of opening cyclodextrin rings to create maltooligosaccharides without showing significant degrading activity toward the resulting maltooligosaccharides. By applying these interesting characteristics of PFTA, the production of valuable maltooligosaccharides, such as maltohexaose, maltoheptaose and maltooctaose, with high degree of purity could be possible at industrial scale.
