中国生物工程杂志

An α-type cyclodextrin glucantransferase was purified to homogeneity by ammonium sulfate precipitation, HiTrap-phenyl column chromatography and HiTrap-Q column chromatography. Molecular weight of the α- cyclodextrin glucantransferase was 75 kDa with an isoelectric point of 5.3. Purified α- cyclodextrin glucantransferase exhibited optimal catalytic temperature of 50°C and optimal catalytic pH of 6.0. Ca2+、Zn2+、Fe3+、Cu2+、Fe2+、Ag+ strongly inhibited enzymatic activity. Km and Vmax values were 50mg/ml and 6.07 mg/ml/min, respectively, using amidulin as substrate. Tryptophan residue was necessary for the catalytic activity. N-terminal amino acid sequence was N-SPDTSVDNKV-. Potato starch was the most suitable substrate for the formation of α-CD. Optimal conditions for preparing α-CD were as follows: 200u/g starch of CGTase, 40°C, 24 hours of incubation. Total conversion yield attained 41% and α-CD occupied about 78% in the products. This work did benefit to the development of α-CD.