Purification and characterization of hydrolytic and transgalactosyl α-galactosidase from Lactobacillus helveticus ATCC 10797

alpha-Galactosidase purified from Lactobacillus helveticus ATCC 10797 by fast performance liquid chromatography system using ion exchange and gel-filtration columns showed the K (m) of 3.83 mM and V (max) of 416.44 A mu mol/min/mg protein calculated from the substrate p-nitrophenyl-alpha-d-galactopyranoside. The molecular mass was 188 kDa by gel-filtration, but 90 kDa by SDS-PAGE, indicating a homodimer. The optimum temperature was 37 A degrees C, and the optimum pH was at 6 with an acceptable stability between pH 4 and 8. This enzyme was activated by 10 mM monovalent ions such as K+, NH4 (+), Li+, and CS+, while the activity was inhibited by divalent ions such as Cu2+, Zn2+, and Fe2+. Melibiose was hydrolyzed to glucose and galactose, raffinose to galactose and sucrose, while stachyose to galactose and sucrose. A novel source of alpha-galactosidase from L. helveticus possessing both hydrolytic activity to eliminate flatulence sugars and transgalactosylation activities to synthesize galacto-oligosaccharides is identified and characterized.