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Genome sequence of the psychrophilic Cryobacterium sp. LW097 and characterization of its four novel cold-adapted β-galactosidases.
International Journal of Biological Macromolecules ( IF 8.2 ) Pub Date : 2020-09-19 , DOI: 10.1016/j.ijbiomac.2020.09.100
Lijun Wang 1 , Yuanzhen Mou 1 , Bo Guan 1 , Youzhen Hu 1 , Yan Zhang 1 , Jun Zeng 2 , Yongqin Ni 1
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A psychrophilic strain Cryobacterium sp. LW097 was isolated from the subglacial sediments and discovered to show considerable β-galactosidases activity at low temperatures. To provide access to genes predicted to encode cold-adapted glycoside hydrolases with biotechnological relevance, we have sequenced the genome of Cryobacterium sp. LW097. Annotation with CAZy database revealed four β-galactosidase genes, bgal322, bgal435, bgal436, and bgal2567 belonging to the GH-42 family and GH-35 family. All the four β-galactosidases recombinantly expressed retained a high level of relative activity at 5 °C and showed different optimum temperatures ranging from 25 °C to 40 °C. The enzyme kinetics proved that Bgal322, Bgal436, and Bgal2567 had lower K m to both oNPG and lactose at 5 °C, further proving their adaption to low temperature. Substrate specificity analysis showed that these four β-galactosidases owned different preferences. The novel GH-35 β-galactosidases Bgal436 showed β-D-glucosidase activity (33.67 ± 0.28%) in addition to β-D-galactosidase activity. Bgal322 preferred β-D-(1,4)-galactobiose, whereas the other three preferred lactulose. Bgal435 showed the highest k cat value of 68.2 ± 1.7 s −1 at 5 °C toward lactose among these four enzymes. The exquisite substrate specificity of Bgal436 in milk made it a potential candidate for applications in milk lactulose quantification.



中文翻译:

嗜冷性低温细菌的基因组序列。LW097及其四个新颖的​​冷适应β-半乳糖苷酶的特性。

嗜冷菌株低温细菌。LW097是从冰川下的沉积物中分离出来的,发现在低温下显示出相当大的β-半乳糖苷酶活性。为了提供可预测具有生物技术相关性的编码冷适应性糖苷水解酶的基因,我们对低温细菌的基因组进行了测序。LW097。CAZy数据库的注释显示了属于GH-42家族和GH-35家族的四个β-半乳糖苷酶基因bgal322bgal435bgal436bgal2567。所有四个β重组表达的β-半乳糖苷酶在5°C时保持较高水平的相对活性,并显示25°C至40°C的不同最佳温度。酶动力学证明Bgal322,Bgal436和Bgal2567具有较低ķ 到两个ö NPG和乳糖在5℃,进一步证明其适配于低的温度。底物特异性分析表明,这四种β-半乳糖苷酶具有不同的偏好。新颖的GH-35 β -galactosidases Bgal436表明β除了-D-葡糖苷酶活性(33.67±0.28%)到β -D-半乳糖苷酶的活性。Bgal322首选β-D-(1,4)-半乳糖二糖,而其他三个优选乳果糖。在这四种酶中,Bgal435在5°C时对乳糖的最高k cat值为68.2±1.7 s -1。Bgal436在牛奶中的优良底物特异性使其成为牛奶乳果糖定量应用的潜在候选者。

更新日期:2020-09-20
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