Sin K A, Nakamura A, Masaki H, Matsuura Y, Uozumi T
Department of Biotechnology, Faculty of Agriculture, University of Tokyo, Japan.
J Biotechnol. 1994 Feb 28;32(3):283-8. doi: 10.1016/0168-1656(94)90214-3.
Cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19) produces cyclodextrin (CD) from starch through an intramolecular transglucosylation reaction. To obtain a better understanding of the amylolytic and cyclization mechanisms of CGTase, and furthermore to improve the production of gamma-CD, mutant CGTases were constructed by site-directed mutagenesis of the CGTase gene of Bacillus ohbensis replacing Tyr at position 188 by 19 other amino acids. All mutant enzymes retained both starch-degrading and CD synthesizing activities to various extents. Among them, a mutant enzyme having Trp instead of Tyr-188 produced 15% of gamma-CD from soluble starch, which is about twice as much as the amount produced by the wild-type enzyme.
环糊精葡糖基转移酶（CGTase；EC 2.4.1.19）通过分子内转糖基化反应从淀粉产生环糊精（CD）。为了更好地理解CGTase的淀粉分解和环化机制，进而提高γ-环糊精的产量，通过对嗜碱芽孢杆菌CGTase基因进行定点诱变，将第188位的酪氨酸替换为其他19种氨基酸，构建了突变型CGTase。所有突变酶都不同程度地保留了淀粉降解和CD合成活性。其中，一种用色氨酸取代第188位酪氨酸的突变酶从可溶性淀粉中产生了15%的γ-环糊精，这大约是野生型酶产量的两倍。
