Abstract: Alpha- galactosidase is a kind of industrial enzyme preparation with a huge commercial value, which has been widely used in medicine, food and chemical industries. A strain of Brachybacterium sp. DB5 was selected to isolate α- galactosidase gene by PCR. Sequencing and BLAST analysises showed that the sequence encoded a α-galactosidase. It was recombinant into the vector pET-30a(+) and transformed into the strain E. coli. α-Galactosidase gene was expressed efficiently after induction with IPTG. An expression activity 5.07 U/mL was obtained. After purification of pure, enzyme activity was 72.78 U/mL. The enzymatic analysis revealed that its optimal pH and temperature were 6.0 and 40℃, respectively. The enzyme could be used for additive of animal feed, soybean meal, in order to improve the feed utilization rate.

Key words: α-galactosidase, Brachybacterium sp., gene cloning, expression, characterization

摘要： α-半乳糖苷酶是一种有着巨大商业价值的工业酶制剂，在医药、食品和化工等行业有着广泛的应用。以来源于雪莲根部土壤的短状杆菌Brachybacterium sp. DB5为材料，从其基因组中扩增出一个α-半乳糖苷酶基因编码序列，经过测序及BLAST比对分析，证实该基因属于α-半乳糖苷酶。将其与pET-30a(+)载体相连后在大肠杆菌中进行异源表达，经过诱导获得了此酶的胞外高效表达，粗酶液的活性为5.07 U/mL，经纯化后酶的活性达72.78 U/mL，酶学特性分析表明其最适pH为6.0，最适温度为40℃。此酶可用作动物饲料豆粕的添加剂，以提高饲料的利用率。

关键词: &alpha, -半乳糖苷酶, 短状杆菌, 基因克隆, 表达, 性质