Abstract
The purification and properties of α-galactosidase from Lactobacillus fermentum are described. This enzyme has different characteristics from those isolated from other microorganisms. Its molecular mass is 194500 Da and it is composed of four subunits of 45 kDa each. α-Galactosidase exhibits a greater affinity for the substrate, p-nitrophenyl-α- d-galactopyranoside ( K m = 0.079 mM and V m = 2838 μmol ml −1 min −1 mg −1). Maximum activity occurred at 45°C and in a pH range of 5.0–6.5. The apparent activation energy, determined according to the Arrhenius plot (12001 cal mol −1) showed a straight line with no inflections in the temperature region between 25 and 45°C. A strong inhibition of α-galactosidase activity was found in the presence of 0.1 mM HgCl 2 and 0.01 mM p-chloromercuribenzoate; however, the enzyme was not affected by CaCl 2, CuSO 4, MnCl 2, FeCl 3, CdCl 2, NaCN, NiSO 4, KCN, FeSO 4 or other chemical products such as EDTA, dithiothreitol and β-mercaptoethanol.
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