Purification and Properties of Gmi Ganglioside β-Galactosidases from Bovine Brain

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Abstract
Two GMi-β-galactosidases,β-galactosidases I, and n, have been highly purified from bovine brain by procedures including acetone and butanol treatments, and chromatographies on Con A-Sepharose, PATG-Sepharose, and Sephadex G-200. β-Galactosidase I was purified 30,000-fold and β-galactosidase H 19,000-fold. Both enzymes appeared to be homogeneous, as judged from the results of polyacrylamide disc gel electrophoresis. Enzyme I had a molecular weight of 600,000–700,000 and enzyme II one of 68,000, as determined on gel filtration. On sodium dodecyl sulfate polyacrylamide slab gel electrophoresis under denaturing conditions, enzyme II gave a single band with a molecular weight of 62,000, while enzyme I gave two minor bands with molecular weights of 32,000 and 20,000 in addition to the major band at 62,000. Both enzymes liberated the terminal galactose from Gmi ganglioside and lactosylceramide but not from galactosylceramide. Enzyme I showed a pH optimum of 4.0 and was heat stable, while enzyme II showed a pH optimum of 5.0 and lost 50% of its activity in 15 min at 45°C. Enzyme I showed a pi of 4.2 and enzyme II one of 5.9.