Saito Katsuichi, Oda Yuji, Tomita Fusao, Yokota Atsushi
Department of Upland Agriculture Research, National Agricultural Research Center for Hokkaido Region, Shinsei, Memuro, Kasai, 082-0071, Hokkaido, Japan.
FEMS Microbiol Lett. 2003 Jan 28;218(2):265-70. doi: 10.1111/j.1574-6968.2003.tb11527.x.
The gene encoding a 2,6-beta-D-fructan 6-levanbiohydrolase (LF2ase) (EC 3.2.1.64) that converts levan into levanbiose was cloned from the genomic DNA of Streptomyces exfoliatus F3-2. The gene encoded a signal peptide of 37 amino acids and a mature protein of 482 amino acids with a total length of 1560 bp and was successfully expressed in Escherichia coli. The similarities of primary structure were observed with levanases from Clostridium acetobutylicum, Bacillus subtilis, B. stearothermophilus (51.0-54.3%) and with LF2ase from Microbacterium levaniformans (53.9%). The enzyme from S. exfoliatus F3-2 shared the conserved six domains and the completely conserved five amino acid residues with family 32 glycosyl hydrolases, which include levanase, inulinase, and invertase. These observations led to the conclusion that the enzyme belongs to family 32 glycosyl hydrolases.
从脱落链霉菌F3-2的基因组DNA中克隆出编码一种将果聚糖转化为蔗果六糖的2,6-β-D-果聚糖6-蔗果六糖水解酶（LF2ase）（EC 3.2.1.64）的基因。该基因编码一个37个氨基酸的信号肽和一个482个氨基酸的成熟蛋白，全长1560 bp，并在大肠杆菌中成功表达。观察到其一级结构与丙酮丁醇梭菌、枯草芽孢杆菌、嗜热脂肪芽孢杆菌的果聚糖酶（51.0 - 54.3%）以及来自类果聚糖微杆菌的LF2ase（53.9%）具有相似性。脱落链霉菌F3-2的这种酶与32家族糖基水解酶（包括果聚糖酶、菊粉酶和转化酶）共有保守的六个结构域和完全保守的五个氨基酸残基。这些观察结果得出该酶属于32家族糖基水解酶的结论。
