Purification of glycoside hydrolases from Bacteroides fragilis

Abstract

Six glycoside hydrolases in the culture medium of B. fragilis (.alpha.-glucosidase, .beta.-glucosidase, .alpha.-galactosidase, .beta.-galactosidase, .beta.-N-acetylglucosaminidase and .alpha.-L-fucosidase) were systematically purified by (NH4)2SO4 precipitation, gel filtration chromatography and density gradient isoelectric focusing. The isoelectric focusing resolved the glycosidases into distinct, well-separated fractions and revealed 3 differently charged forms of .beta.-N-acetylglucosaminidase and of .alpha.-L-fucosidase. .alpha.-Glucosidase and .beta.-N-acetylglucosaminidase possessed dual affinities for the respective galactoside substrates; .beta.-galactosidase also hydrolyzed .beta.-D-fucoside. .alpha.-Glucosidase was purified to homogeneity as indicated by a thin-layer isoelectric focusing zymogram technique. The glycosidases, with exception of .beta.-glucosidase and the acid .alpha.-L-fucosidase, were each separated from other glycosidic activities to 99%. The MW were 58,000-125,000. The pH optima ranged from 4.8-6.9.