A cell wall-bound beta-glucosidase from germinated rice: purification and properties.
A large portion of beta-glucosidase (EC 3.2.1.21) in germinating rice seeds, which appears to be ionically bound to cell walls, can be solubilized with 1 M NaCl. Its activity increased more than eight-fold within five days of germination. It was purified to electrophoretic homogeneity from the extracts of germinated rice seeds by fractionation with (NH4)2SO4 followed by CM-Sepharose, Polybuffer exchanger 118, Concanavalin A-Sepharose and Bio-Gel P-100. The Mr of the purified enzyme, estimated by SDS-PAGE, was 56,000 and the isoelectric point was > 10.0. Its N-terminal amino acid sequence (44 residues) exhibited high homology to those of beta-glucosidases from other plants, such as barley and white clover. Its activity was optimal at pH 4.5 and 50 degrees, and it was strongly inhibited by glucono-1,5-lactone. The enzyme showed hydrolytic as well as transglycosylation activity towards (1-->3)-beta- and (1-->4)-beta-linked oligosaccharides with degree of polymerization of 2-4. The results suggest that the beta-glucosidase is probably involved not only in hydrolysis but also in modification of oligosaccharides in cell walls of germinating rice seeds.
Akiyama
T
T
National Hokkaido Agricultural Experiment Station, Sapporo, Japan. takiyama@cryo.affrc.go.jp
Kaku
H
H
Shibuya
N
N
D000595:Amino Acid Sequence; D002473:Cell Wall / Q000201:enzymology*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism
D001617:beta-Glucosidase