Purification and characterization of β-galactosidase from leaves of Zizyphus oenoplia

Abstract

A novel β-galactosidase was purified to homogeneity, from Zizyphus oenoplia leaves, using chilled acetone precipitation followed by ammonium sulphate precipitation and affinity chromatography on cross linked g uar-gum. The enzyme was a monomeric with a molecular weight of about 23 kDa on SDS-PAGE. It was active between pH 4 - 7, with an optimum activity at pH 5.5, and was fairly stable from pH 4.5 to 8.0. The enzyme showed optimum activity at 37° and was stable up to 80 °.  The presence of metal ions such as Mg++ and Mn++ positively influenced the activity of β-galactosidase but the activity was inhibited in the presence of Cd++, Hg++ and Pb++. The enzyme showed maximum activity towards β – oNPGal, the substrate α – pNPGal.