A cold-adapted amylase-generated bacterium GXBC-1 was isolated from starch-pile by dilution method , which was preliminarily identified as Bacillus cereus . CXBC-1 . Amylase gene was amplified by polymerase chain reaction (PCR) . Nucleotide sequence analysis showed that the amyGXBC-1 gene was composed of 1764 bp (588 amino acid residues with Mw of 64 kD) . The characteristics of the cold-adapted amylase were also discussed .The optimum temperature for the amylase was 35℃ and the optimum pH was 7.0. Even at 20℃, the enzyrue still showed 53％ enzyme activity .But the amylase was not stable above 50℃. Its Km was 0.72 mg/mL . The results of HPLC of products from starch demonstrated that this enzyme, without the activity of incision enzyme , should be classified as (β-arnylase .%从废弃的淀粉堆中筛选到一株产低温淀粉酶的蜡样芽孢杆菌(Bacillus cereus)GXBC-1,通过同源保守序列比对,从中克隆到一个淀粉酶基因.该基因全长为1764bp,编码588个氨基酸,分子量约为64kD.将基因克隆到大肠杆菌进行表达及酶学性质研究,该重组酶最适温度为35℃,在20℃仍具有53%的活力;最适pH值为7.0,Km值为0.72 mg/mL.产物经HPLC分析,该酶没有内切酶活性,具有典型的β-淀粉酶特性.
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