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Publication Abstract from PubMed

A novel gene was isolated for the first time from a psychrophilic gram-negative bacterium Rahnella sp. R3. The gene encoded a cold-adapted beta-galactosidase (R-beta-Gal). Recombinant R-beta-Gal was expressed in Escherichia coli BL21 (DE3), purified and characterized. R-beta-gal belongs to the glycosyl hydrolase family 42. Circular dichroism spectrometry of the structural stability of R-beta-Gal with respect to temperature indicated that the secondary structures of the enzyme were stable to 45 degrees C. In solution, the enzyme was a homo-trimer and was active at temperatures as low as 4 degrees 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 degrees C. These values were lower than the corresponding K(m)s reported for other cold-adapted beta-Gals.

Cloning, expression and structural stability of a cold-adapted beta-galactosidase from Rahnella sp. R3.,Fan Y, Hua X, Zhang Y, Feng Y, Shen Q, Dong J, Zhao W, Zhang W, Jin Z, Yang R Protein Expr Purif. 2015 Nov;115:158-64. doi: 10.1016/j.pep.2015.07.001. Epub, 2015 Jul 3. PMID:26145832^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.