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  • Title: Cloning, expression and structural stability of a cold-adapted β-galactosidase from Rahnella sp. R3.
    Author: Fan Y, Hua X, Zhang Y, Feng Y, Shen Q, Dong J, Zhao W, Zhang W, Jin Z, Yang R.
    Journal: Protein Expr Purif; 2015 Nov; 115():158-64. PubMed ID: 26145832.
    Abstract:
    A novel gene was isolated for the first time from a psychrophilic gram-negative bacterium Rahnella sp. R3. The gene encoded a cold-adapted β-galactosidase (R-β-Gal). Recombinant R-β-Gal was expressed in Escherichia coli BL21 (DE3), purified and characterized. R-β-gal belongs to the glycosyl hydrolase family 42. Circular dichroism spectrometry of the structural stability of R-β-Gal with respect to temperature indicated that the secondary structures of the enzyme were stable to 45°C. In solution, the enzyme was a homo-trimer and was active at temperatures as low as 4°C. The enzyme did not require the presence of metal ions to be active, but Mg(2+), Mn(2+), and Ca(2+) enhanced its activity slightly, whereas Fe(3+), Zn(2+) and Al(3+) appeared to inactive it. The purified enzyme displayed K(m) values of 6.5 mM for ONPG and 2.2mM for lactose at 4°C. These values were lower than the corresponding K(m)s reported for other cold-adapted β-Gals.
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