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|標題:||Role of the C-terminal domain of Thermus thermophilus trehalose synthase in the thermophilicity, thermostability, and efficient production of trehalose|
|期刊/報告no：:||Journal of Agricultural and Food Chemistry, Volume 55, Issue 9, Page(s) 3435-3443.|
|摘要:||Trehalose synthase (TS) from Thermus thermophilus (TtTS) is a thermostable enzyme that catalyzes the conversion of maltose into trehalose by intramolecular transglucosylation. It has a relatively higher thermophilicity and thermostability and a better conversion ratio for trehalose production than other known TSs from different sources at present. By amino acid sequences and the schematic motif alignment of trehalose synthase-related enzymes, it was found that TtTS (965 amino acid residues) contains a particular C-terminal fragment that is not found in most other TSs. To verify the function of this fragment, C-terminal deletion and enzyme fusion were respectively performed to explain the important role this fragment plays in the formation of trehalose. First, the C terminus (TtTS Delta N, 415 amino acid residues) of TtTS is deleted to construct a TtTS Delta C containing 550 amino acids. Furthermore, a novel cold-active TS was cloned and purified from Deinococcus radiodurans (DrTS, 552 amino acid residues) and then a fusion protein was created with TtTS Delta N at the C terminus of DrTS (DrTS-TtTS Delta N). It was found that the recombinant TtTS Delta C enzyme had a lower thermostability and a higher byproduct than TtTS in catalyzing the conversion of maltose into trehalose. On the other hand, the recombinant DrTS-TtTS Delta N enzyme had a higher thermostability and a lower byproduct than DrTS in their reactions. The above-mentioned results allowed the inference that the C terminus of TtTS plays a key role in maintaining its thermostability and hence in modulating the side reaction to reduce glucose production at a high temperature. A new, simple, and fast method to improve thermophilicity by fusing this fragment with particular conformation to a thermolabile enzyme is offered.|
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