Characterization and kinetics of beta-D-gluco/fuco/galactosidase from sheep liver.
This enzyme shows beta-D-glucosidase, beta-D-fucosidase and beta-D-galactosidase activities, all associated in a single peak in Sephadex G-200, DEAE-cellulose, concanavalin A-Sepharose chromatographies, and in high resolution isoelectric focusing (pI 4.56), having the optimal pH in the range 4.5-5.5. The enzyme is very stable under different conditions: (i) at pH in the range 5.5-7.0; (ii) in successive freezing-thawing cycles; (iii) at 4 degrees C; (iv) after exhaustive ultrasonic treatment. It is not stable beyond 40 degrees C, and in the presence of urea, Triton X-100, SDS or mercaptoethanol. HgCl2, KCN, Tris, maltose and the lactones were inhibitors of the enzyme. With glucose, fucose and galactose the inhibition is competitive. In addition, a transglycosylation mechanism seems to occur. The kinetic studies suggest a substrate-activation model and the presence of two primary active sites: fuco-gluco and galacto.
D000818:Animals; D005696:Galactosidases / Q000378:metabolism*; D005959:Glucosidases / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007525:Isoelectric Focusing; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D012756:Sheep; D014465:Ultrasonics; D005644:alpha-L-Fucosidase / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism*; D001617:beta-Glucosidase / Q000378:metabolism*
D005696:Galactosidases; D005959:Glucosidases; D001617:beta-Glucosidase; D001616:beta-Galactosidase; C028219:beta-D-fucosidase; D005644:alpha-L-Fucosidase