DNA polymerases are widely used in PCR and play important roles in life science research and related fields. Development of high-performance DNA polymerases is of great commercial interest as the current commercial DNA polymerases could not fully satisfy the requirements of scientific research. In this study, we cloned and expressed a family B DNA polymerase (NCBI accession number TEU_RS04875) from Thermococcus eurythermalis A501, characterized its enzymatic property and evaluated its application in PCR. The recombinant Teu-PolB was expressed in E. coli and purified with affinity chromatography and ion-exchange chromatography. The enzymatic properties of Teu-PolB were characterized using fluorescence-labeled oligonucleotides as substrates. The application potential of Teu-PolB in PCR was evaluated using the phage λ genomic DNA as a template. Teu-PolB has DNA polymerase and 3'→5' exonuclease activities, and is highly thermostable with a half-life of 2 h at 98 ℃. The most suitable PCR buffer is consisted of 50 mmol/L Tris-HCl pH 8.0, 2.5 mmol/L MgCl₂, 60 mmol/L KCl, 10 mmol/L (NH₄)₂SO₄, 0.015% Triton X-100 and 0.01% BSA, and the optimal extension temperature is 68 ℃. Under the optimized conditions, a 4 kb target fragment was successfully amplified with an extension rate of 2 kb/min. The yield of the Teu-PolB amplified-DNA was lower than that of Taq DNA polymerase, but its extension rate and fidelity was higher than that of Taq and Pfu DNA polymerases. The biochemical properties of Teu-PolB demonstrate that this enzyme can be used in PCR amplification with high thermostability, good salt tolerance, high extension rate and high fidelity.
DNA-Directed DNA Polymerase/genetics* ; Escherichia coli/genetics* ; Polymerase Chain Reaction/methods* ; Temperature ; Thermococcus/genetics*

Cyclodextrin glucanotransferase, the essential enzyme for the production of cyclodextrins, has become the focus of scientific research nowadays. Although many related enzyme properties are well known, the crucial factors in product specificity determination remain to be answered. Here, the recent research progresses of cyclodextrin glucanotransferase, especially those about the evolution of product specificity, were reviewed, and the scientific problems were discussed.
Archaeal Proteins ; genetics ; metabolism ; Bacillus ; enzymology ; genetics ; Bacterial Proteins ; genetics ; metabolism ; Biocatalysis ; Cyclodextrins ; metabolism ; Evolution, Molecular ; Glucosyltransferases ; classification ; genetics ; metabolism ; Mutation ; Thermoanaerobacterium ; enzymology ; genetics ; Thermococcus