| 论文题目: | Cloning, expression, and characterization of a thermostable glucoamylase from Thermoanaerobacter tengcongensis MB4. |
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| 作者: | Yingying Zheng, Yanfen Xue, Yueling Zhang, Cheng Zhou, Ulrich Schwaneberg*, Yanhe Ma* |
| 联系作者: | 马延和 |
| 刊物名称: | Applied Microbiology and Biotechnology |
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| 年份: | 2010 |
| 影响因子: | 2.896 |
| 论文下载: | |
| 摘要: | A thermostable glucoamylase (TtcGA) from Thermoanaerobacter tengcongensis MB4 was successfully expressed in Escherichia coli. The full-length gene (2112 bp) encodes a 703-amino acid polypeptide including a predicted signal peptide of 21 residues. The recombinant mature protein was partially purified to 30-fold homogeneity by heat treatment and gel filtration chromatography. The mature protein is a monomer with the molecular weight of 77 kD. The recombinant enzyme showed maximum activity at 75 °C and pH 5.0. It is the most thermostable bacterial glucoamylase described to date with nearly no activity loss after incubation at 75 °C for 6 h. TtcGA can hydrolyze both α-1, 4- and α-1, 6-glycosidic linkages in various α-glucans. It showed preference for maltooligosaccharides over polysaccharides with specific activity of 80 U/mg towards maltose. Kinetic studies revealed that TtcGA had the highest activity on maltooligosaccharide with four monosaccharide units. The cations Ca2+, Mn2+, Co2+, Mg2+, and reducing agent DTT showed no obvious effects on the action of TtcGA. In contrast, the enzyme was inactivated by Zn2+, Pb2+, Cu2+, and EDTA. |
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