Abstract
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, gal42, was cloned from a newly isolated marine bacterium Bacillus sp. BY02 and expressed in Escherichia coli. 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 Zn2+ (229.6%) and other divalent metal ions (Mn2+, Mg2+, and Co2+), 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.
Highlights
Lactose intolerance is one of the most common nutritional disorders, with 70% of the world’s population affected by it (Horner et al, 2011; Di Costanzo and Berni Canani, 2018)
The productivity of β-galactosidases from natural microbial cells hardly meets the needs of industrial application due to the low yield (Park and Oh, 2010; Oliveira et al, 2011)
Boosting the reaction efficiency of β-galactosidases is a precondition for achieving its industrial application
Summary
Lactose intolerance is one of the most common nutritional disorders, with 70% of the world’s population affected by it (Horner et al, 2011; Di Costanzo and Berni Canani, 2018). Removal of lactose from milk by the conversion of lactose to D-glucose and D-galactose is of great value for lactose-intolerant people. Β-Galactosidase (EC 3.2.1.23), referred to as lactase, is an important member of glycosyl hydrolase, which can hydrolyze O-glycosidic bonds of lactose by hydrolysis reaction, resulting in the production of glucose and galactose (Vera et al, 2017; Singh et al, 2019). Numerous β-galactosidases were purified, cloned, and characterized from bacteria (Mavromatis et al, 2010; Tian et al, 2013), fungi (Rico-Díaz et al, 2017), yeast (de Freitas et al, 2020), plants (Deng et al, 2019), and mammals (He et al, 2008).
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