Genome sequence of the psychrophilic Cryobacterium sp. LW097 and characterization of its four novel cold-adapted beta-galactosidases

文献类型： 外文期刊

第一作者： Wang, Lijun

作者： Wang, Lijun;Mou, Yuanzhen;Guan, Bo;Hu, Youzhen;Zhang, Yan;Ni, Yongqin;Zeng, Jun

作者机构：

关键词： Cold-adapted beta-galactosidases; Cryobacterium sp.; Psychrophilic bacterium; Cold-adaption; Lactose hydrolysis; Glacier

期刊名称：INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES （ 影响因子：6.953； 五年影响因子：6.737 ）

ISSN： 0141-8130

年卷期： 2020 年 163 卷

页码：

收录情况： SCI

摘要： A psychrophilic strain Cryobacterium sp. LW097 was isolated from the subglacial sediments and discovered to show considerable beta-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 beta-galactosidase genes, bgal322, bgal435, bgal436, and bgal2567 belonging to the GH-42 family and GH-35 family. All the four beta-galactosidases recombinantly expressed retained a high level of relative activity at 5 degrees C and showed different optimum temperatures ranging from 25 degrees C to 40 degrees C. The enzyme kinetics proved that Bgal322, Bgal436, and Bgal2567 had lower K-m to both oNPG and lactose at 5 degrees C, further proving their adaption to low temperature. Substrate specificity analysis showed that these four beta-galactosidases owned different preferences. The novel GH-42 beta-galactosidases Bgal435 showed beta-D-glucosidase activity (33.67 +/- 0.28%) in addition to beta-D-galactosidase activity. Bgal322 preferred beta-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 degrees 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. (C) 2018 Elsevier B.V. All rights reserved.

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