title: Purification and characterization of two novel beta-galactosidases from Lactobacillus reuteri.
abstract: The intracellular beta-galactosidase (beta-gal) enzymes from two strains of Lactobacillus reuteri, L103 and L461, were purified by ammonium sulfate fractionation, hydrophobic interaction, and affinity chromatography. Both enzymes are heterodimers with a molecular mass of 105 kDa, consisting of a 35 kDa subunit and a 72 kDa subunit. Active staining of L. reuteri L103 and L461 beta-gal with 4-methylumbelliferyl beta-d-galactoside showed that the intact enzymes as well as the larger subunits possess beta-galactosidase activity. The isoelectric points of L. reuteri L461 and L103 beta-gal were found to be in the range of 3.8-4.0 and 4.6-4.8, respectively. Both enzymes are most active in the pH range of 6-8; however, they are not stable at pH 8. The L. reuteri beta-galactosidases are activated by various mono- and divalent cations, including Na(+), K(+), and Mn(2+), and are moderately inhibited by their reaction products d-glucose and d-galactose. Because of their origin from beneficial and potentially probiotic lactobacilli, these enzymes could be of interest for the synthesis of prebiotic galacto-oligosaccharides.
authors.affiliation: Research Centre Applied Biocatalysis, Petersgasse 14, A-8010 Graz, Austria, Division of Food Biotechnology, Muthgasse 18, A-1190 Vienna, Austria.
authors.forename: Thu-Ha
authors.initials: TH
authors.lastname: Nguyen
authors.forename: Barbara
authors.initials: B
authors.lastname: Splechtna
authors.forename: Marlene
authors.initials: M
authors.lastname: Steinböck
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kneifel
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Lettner
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Kulbe
authors.forename: Dietmar
authors.initials: D
authors.lastname: Haltrich
mesh_terms: D002412:Cations; D019281:Dimerization; D004795:Enzyme Stability; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D052200:Limosilactobacillus reuteri / Q000201:enzymology*; D008970:Molecular Weight; D001616:beta-Galactosidase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D002412:Cations; D001616:beta-Galactosidase