Zhou Zihan, He Ningning, Han Qi, Liu Songshen, Xue Ruikun, Hao Jianhua, Li Shangyong
School of Basic Medicine, Qingdao University, Qingdao, China.
Key Laboratory of Sustainable Development of Polar Fishery, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.
Front Microbiol. 2021 Oct 25;12:742300. doi: 10.3389/fmicb.2021.742300. eCollection 2021.
β-Galactosidase plays an important role in medicine and dairy industry. In this study, a new glycoside hydrolase family 42 (GH42) β-galactosidase-encoding gene, , was cloned from a newly isolated marine bacterium sp. BY02 and expressed in . Structural characterization indicated that the encoding β-galactosidase, Gal42, is a homotrimer in solution, and homology modeling indicated that it retains the zinc binding sites of the Cys cluster. The reaction activity of Gal42 was significantly increased by Zn (229.6%) and other divalent metal ions (Mn, Mg, and Co), while its activity was inhibited by EDTA (53.9%). Meanwhile, the thermo-stability of the Gal42 was also significantly enhanced by 5 and 10 mM of zinc ion supplement, which suggested that the "Cys-Zn" motif played important roles in both structural stability and catalytic function. Furthermore, Gal42 showed effective lactose hydrolysis activity, which makes the enzyme hydrolyze the lactose in milk effectively. These properties make Gal42 a potential candidate in food technology.
β-半乳糖苷酶在医学和乳制品行业中发挥着重要作用。在本研究中，从新分离的海洋细菌 sp. BY02 中克隆了一个新的糖苷水解酶家族42（GH42）β-半乳糖苷酶编码基因，并在 中表达。结构表征表明，编码的β-半乳糖苷酶Gal42在溶液中是同源三聚体，同源建模表明它保留了半胱氨酸簇的锌结合位点。Gal42的反应活性通过锌（229.6%）和其他二价金属离子（锰、镁和钴）显著提高，而其活性受到EDTA（53.9%）的抑制。同时，通过补充5和10 mM的锌离子，Gal42的热稳定性也显著增强，这表明“半胱氨酸-锌”基序在结构稳定性和催化功能中都发挥着重要作用。此外，Gal42表现出有效的乳糖水解活性，这使得该酶能够有效水解牛奶中的乳糖。这些特性使Gal42成为食品技术中的一个潜在候选者。
