Li Y, Ferenci T
Department of Microbiology G08, University of Sydney, New South Wales, Australia.
Microbiology (Reading). 1996 Jul;142 ( Pt 7):1651-7. doi: 10.1099/13500872-142-7-1651.
The complete nucleotide sequence of the surA gene, encoding a sucrase from Bacillus stearothermophilus NUB36, was determined. surA was composed of 1338 bp and encoded 445 amino acid residues. The deduced polypeptide of M(r) 51519 showed strong sequence similarity to sucrose and sucrose phosphate hydrolases from Bacillus subtilis, Klebsiella pneumoniae and Vibrio alginolyticus, and contained the 'sucrose box' residues thought to be important for catalysis of the transfer of fructose from sucrose. The enzyme was partially purified using affinity chromotography from extracts of Escherichia coli containing the cloned surA. SurA displayed an optimum temperature for sucrose hydrolysis of 55 degrees C and high stability. The M(r) of SurA determined by gel filtration was 105,000, which suggested that the active form of the enzyme is a dimer. SurA exhibited an apparent Km of 40 mM for sucrose but, unlike the homologous B. subtilis enzyme, had no detectable sucrose phosphate hydrolase activity.
测定了嗜热脂肪芽孢杆菌NUB36蔗糖酶编码基因surA的完整核苷酸序列。surA由1338个碱基对组成，编码445个氨基酸残基。推导的分子量为51519的多肽与枯草芽孢杆菌、肺炎克雷伯菌和溶藻弧菌的蔗糖和蔗糖磷酸水解酶具有很强的序列相似性，并且含有被认为对催化蔗糖中果糖转移很重要的“蔗糖盒”残基。使用亲和色谱法从含有克隆的surA的大肠杆菌提取物中对该酶进行了部分纯化。SurA对蔗糖水解的最适温度为55℃，且具有高稳定性。通过凝胶过滤测定的SurA的分子量为105,000，这表明该酶的活性形式是二聚体。SurA对蔗糖的表观Km为40 mM，但与同源的枯草芽孢杆菌酶不同，没有可检测到的蔗糖磷酸水解酶活性。
